Systems and methods for coherent optics interface

ABSTRACT

A communication network includes a coherent optics transmitter, a coherent optics receiver, an optical transport medium operably coupling the coherent optics transmitter to the coherent optics receiver, and a coherent optics interface. The coherent optics interface includes a lineside interface portion, a clientside interface portion, and a control interface portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application Ser. No. 62/585,640, filed Nov. 14, 2017, which isincorporated herein by reference in its entirety.

BACKGROUND

The field of the disclosure relates generally to communication networks,and more particularly, to communication interfaces for access networkscapable of transporting signals according to one or more networkprotocols.

Most network operators have very limited fiber available between theheadend (HE)/hub and the fiber node to use for data and video services,often only just 1-2 fiber strands. With end users demanding morebandwidth to the home, operators need a strategy on how to increasecapacity in the access network. One way is to add more fiber between theHE/hub and the fiber node, but retrenching is costly and time consuming,so return on investment (RoI) makes this option unattractive; a solutionthat re-uses the existing infrastructure would be preferred. The bestuse of the existing infrastructure to meet the bandwidth demand whileavoiding the retrenching costs is to use point-to-point (P2P) coherentoptics along with wavelength division multiplexing (WDM) in the accessnetwork.

Coherent optics technology is becoming common in the subsea, long-haul,and metro networks, but has not yet been applied to access networks.However, it is desirable to utilize coherent optics technology in theaccess network because the distances from the HE/hub to the fiber nodeare much shorter in coherent optics networks in comparison with othertypes of networks. It is therefore desirable to provide coherent opticssystems and methods for the access network realize a larger margin foradding more compact wavelengths, due to the signal-to-noise (SNR)improvements in that would result. By adapting coherent opticstechnology to the access network, some of the modules used in othernetworks, to conduct distortion compensation, nonlinear compensation,and error correction, may be eliminated, simplified, and/or implementedusing components with relaxed requirements, thereby resulting insignificant cost savings for a P2P coherent optic link implementation.

SUMMARY

In an embodiment, a communication network includes a coherent opticstransmitter, a coherent optics receiver, an optical transport mediumoperably coupling the coherent optics transmitter to the coherent opticsreceiver, and a coherent optics interface. The coherent optics interfaceincludes a lineside interface portion, a clientside interface portion,and a control interface portion.

BRIEF DESCRIPTION

These and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic illustration of a cable network accessarchitecture.

FIG. 2 is a schematic illustration of a centralized converged cableaccess platform architecture.

FIG. 3 is a schematic illustration of a fiber deep node architecture.

FIG. 4 is a schematic illustration of a fiber deep node architecture.

FIG. 5 is a schematic illustration of a remote network architecture.

FIG. 6 is a schematic illustration of a passive optical networkarchitecture.

FIG. 7 is a schematic illustration of a remote passive optical networkarchitecture.

FIG. 8 is a schematic illustration of a network architecture.

FIG. 9 is a schematic illustration of a network architecture.

FIG. 10 is graphical illustration of a service bandwidth growth plot.

FIG. 11 is graphical illustration depicting a polarization multiplexingeffect.

FIG. 12 is graphical illustration depicting a visualization of a datachannel.

FIG. 13 is a schematic illustration of a coherent network architecture.

FIG. 14 depicts a spectral band diagram.

FIG. 15 is a schematic illustration of a coherent optics link subsystem.

FIG. 16 is a schematic illustration of the coherent optics linksubsystem.

FIG. 17 is a schematic illustration of a coherent optics link subsystem.

FIG. 18 is a schematic illustration of a coherent optics link subsystem.

FIG. 19 is a schematic illustration of a network architecture 4Apoint-to-point coherent link.

FIG. 20 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 21 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 22 is a schematic illustration of a migrated coherent opticsnetwork architecture.

FIG. 23 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 24 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 25 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 26 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 27 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 28 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 29 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 30 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 31 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 32 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 33 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 34 is a schematic illustration of a coherent optics networkarchitecture.

FIG. 35 is a schematic illustration of a coherent interface subsystem.

FIG. 36 is a graphical illustration depicting a symbol mappingconstellation.

FIG. 37 is a graphical illustration depicting a pulse shaping effect.

FIG. 38 is a schematic illustration of a transmitter.

FIG. 39 is a schematic illustration of a scrambling unit.

FIG. 40 is a schematic illustration of a filter.

FIG. 41 is a schematic illustration of a pre-equalizer unit.

FIG. 42 is a schematic illustration of a receiver.

Unless otherwise indicated, the drawings provided herein are meant toillustrate features of embodiments of this disclosure. These featuresare believed to be applicable in a wide variety of systems including oneor more embodiments of this disclosure. As such, the drawings are notmeant to include all conventional features known by those of ordinaryskill in the art to be required for the practice of the embodimentsdisclosed herein.

DETAILED DESCRIPTION

In the following specification and claims, reference will be made to anumber of terms, which shall be defined to have the following meanings.

The singular forms “a,” “an,” and “the” include plural references unlessthe context clearly dictates otherwise.

“Optional” or “optionally” means that the subsequently described eventor circumstance may or may not occur, and that the description includesinstances where the event occurs and instances where it does not.

As used herein, unless specified to the contrary, “modem terminationsystem,” or “MTS′” may refer to one or more of a cable modem terminationsystem (CMTS), an optical network terminal (ONT), an optical lineterminal (OLT), a network termination unit, a satellite terminationunit, and/or other termination devices and systems. Similarly, “modem”may refer to one or more of a cable modem (CM), an optical network unit(ONU), a digital subscriber line (DSL) unit/modem, a satellite modem,etc.

As used herein, the term “database” may refer to either a body of data,a relational database management system (RDBMS), or to both, and mayinclude a collection of data including hierarchical databases,relational databases, flat file databases, object-relational databases,object oriented databases, and/or another structured collection ofrecords or data that is stored in a computer system.

Furthermore, as used herein, the term “real-time” refers to at least oneof the time of occurrence of the associated events, the time ofmeasurement and collection of predetermined data, the time for acomputing device (e.g., a processor) to process the data, and the timeof a system response to the events and the environment. In theembodiments described herein, these activities and events occursubstantially instantaneously.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about,” “approximately,” and “substantially,” are notto be limited to the precise value specified. In at least someinstances, the approximating language may correspond to the precision ofan instrument for measuring the value. Here and throughout thespecification and claims, range limitations may be combined and/orinterchanged; such ranges are identified and include all the sub-rangescontained therein unless context or language indicates otherwise.

The embodiments described herein provide innovative cable access networkarchitectures that are particular useful for the growing access networktrends in the field. The present systems and methods leverage coherentoptics, and particularly with respect to P2P systems, to significantlyimprove the cable access network, as well as access networks in general.According to the present techniques, the link loss budgets for P2Pcoherent optics transceivers are also significantly improved, and for awide variety of different use cases.

FIG. 1 is a schematic illustration of a cable network accessarchitecture 100. Architecture 100 includes a long haul or backbonenetwork 102 that interconnects different metropolitan areas or regionsin which an operator provides service. Architecture 100 further includesa metro or regional network 104 that provides interconnection to one ormore hubs 106. One or more hubs 106 are deployed by the operator in acontiguous geographic area, such as, for example, an entire metropolitanarea or state, or portions thereof. An access network 108 providesconnection to a plurality of end users 110. End users 110 may includeresidential customers, business customers, small cells or base stationbackhaul-front-haul. Access network further includes plurality of nodes112, amplifiers (not shown), or taps, that are interconnected by atransmission medium 114 to provide service to endpoints 110.Transmission medium 114 may be a fiber, coaxial cables, or othersuitable means for signal transmission. Specific references any specifictype of transmission medium (e.g. a fiber) herein should not beconstrued as limiting and are provided for illustrative purposes, unlessotherwise indicated.

In operation of architecture 100, some components (not shown) at hub 106generate radio frequency (RF) signals that are converted to opticalsignals, which hub 106 transmits over transmission medium 114 (e.g., anoptical fiber) to node 112 (e.g., a fiber node) utilizing analog optics.Node 112 converts the optical signals back to RF/electrical signals thatnode 112 transmits over coaxial cable to endpoints 110. In someembodiments, the RF signal requires amplification several times using RFamplifiers (not shown in FIG. 1) to reach endpoints 110.

Most cable operators run a centralized network that includes head ends,hubs, and fiber nodes. This centralized architecture originallytransmitted downstream video to cable subscribers, but then evolved intoa data over cable network as defined by Data over Cable ServiceInterface Specification (DOCSIS) that introduced cable modem terminationsystem (CMTS) in the headend and the cable modem (CM) at the customerpremises. This centralized architecture originally provided internetaccess and video delivery on the same coaxial cable. The Video EdgeQAM(EQAM) was introduced into the HE/Hub to enable digital video,video-on-demand (VOD), and switched-digital-video. EQAMs evolved tosupport the modulation of both MPEG video and DOCSIS data onto the wireusing a Modular Headend Architecture (MHA-TR). The CMTS and EQAMcontinued to evolve into the converged cable access platform (CCAP) thatprovided higher densities of EQAM and CMTS combined together into thesame chassis; other technologies like Ethernet optics and Ethernetpassive optical network (EPON) theoretically may share the same chassisas well. As a result, the CCAP enabled data, voice, and video to behandled over IP before being converted to RF or optical signals[CCAP-ARCH].

FIG. 2 is a schematic illustration of a centralized architecture 200.Architecture 200 is a centralized CCAP, which has a hybrid fiber-coaxial(HFC) architecture. Architecture 200 includes a hub 202, a node 204, anda transport medium 206 communicatively coupled therebetween. Transportmedium 206 may be an optical fiber. Architecture 200 also includes aplurality of end users 208 downstream from node 204 and a shorttransport medium 210 communicatively coupled between node 204 and enduser 208. A plurality of amplifiers 212 (e.g., including deep nodes) arecommunicative coupled between node 204 and end user 208 by shorttransport medium 210. Hub 202 further include a MTS 214 and a router216.

In operation of architecture 200, the CMTS at hub 202 generates RFsignals to node 204 over analog optics. From node 204, there are one ormore amplifiers 212 in cascade. Typical HFC networks have a relativelysmall number (e.g., 6 to 8) of fiber strands 206 dedicated to each node204. In some cases though, fibers 206 may be repurposed for otherservices or node splitting, which usually leaves 1-2 strands availablefor the original node 206 to support video and data services.Architecture 200 may support about 400 to 500 households per node 206.

As bandwidth demands increased, one approach utilized by cable operatorsto increase capacity has been to split each node into multiple nodes,referred to as node splits. With each node split, the number ofamplifiers between the node and the end of the coaxial plant typicallydecreases. Eventually operators can reach a point where there is only asingle amplifier between the fiber node and the end of the plant (knownas N+1), or there are no more amplifiers at all (known as N+0 or PassiveCoax). This both reduces the number of customers sharing the capacityavailable from that that node, and also reduces the amount of RF noiseintroduced by amplifiers.

Collectively, when a node reaches N+1 or N+0, it is referred to as adeep node, or a fiber deep node. The reason for this is that while somenode splits can be made at the existing node location by segmenting theexisting coaxial plant, eventually it becomes necessary to push thosefiber nodes—and the fiber that supports them—deeper into the network.

FIG. 3 is a schematic illustration of a fiber deep node architecture300. In this description, and for the embodiments that follow, likefeatures are referred to similarly to like features in architecture 200(FIG. 2). Architecture 300 is a deep node architecture. Similar toarchitecture 200, architecture 300 includes a hub 302, a transportmedium 306, a plurality of end users 308, a plurality of short transportmedia 310, and a MTS 314. Different from the configuration illustratedin FIG. 2, architecture 300 includes a plurality of deep nodes 312communicatively coupled to transport medium 306 downstream of hub 302.Deep nodes 312 are communicatively coupled to respective end user 308through short transport media 210. Architecture 300 may also include anoriginal node (not shown).

As illustrated in FIG. 3, in cases where there are extra strands offiber 306 at the original node (not shown) are not in use, these strandscan be repurposed and extended out to the deep nodes 312. The thick lineof fiber 306 extending from hub 302 to deep nodes 312 gets thinner as itadds each deep node 312 to represent multiple fibers 306 from hub 302being extended to fiber 306 at each node 312. By extending fiber 306 todeep node 312, the bandwidth is increased deeper into the accessnetwork. Since a fiber deep node 312 has fewer end users 308 to serve,it has more capacity available to those end users 308. In thisinstantiation, the bandwidth limit is that of fiber(s) 306 at the deepnode 312.

FIG. 4 is a schematic illustration of a fiber deep node architecture400. Architecture 400 is a deep node architecture that includes awavelength multiplexer, and is similar to, in some respects,architecture 300. Architecture 400 includes a hub 402, a node 404, atransport medium 406, a plurality of end users 408, a plurality of shorttransport media 410, a plurality of deep nodes 412, and a MTS 414.Different from the configuration illustrated in FIG. 3, architecture 400further includes a multiplexer 418 communicatively coupled to MTS 414and transport medium 406 at hub 402 and a demultiplexer 420commutatively coupled to transport medium 406 at node 404. Node 404 may,for example, be an optical distribution center (ODC).

As described above, there is limited fibers 406 available between node404 location and hub 402. In order to support multiple deep nodes 412where before there was only one, some type of wavelength divisionmultiplexing (WDM) may be used to support multiple wavelengths, one foreach of new deep node 412. As shown in FIG. 4, in some embodiments,multiplexer 418 may be used to aggregate multiple wavelengths onto asingle fiber or fiber pair, allowing multiple nodes 404, 412 to sharethe same fiber 406 connecting to hub 402. It should be noted that withanalog optics, the link between hub 402 and ODC 404 is most commonlyfour wavelengths, but could be up to 16 wavelengths for shorterdistances. This limited number of wavelengths is due to the noisegenerated by the analog signals, which require larger spacing betweeneach wavelength to prevent inter-channel interference. Therefore, thisis the practical maximum capacity for analog wavelengths from hub 402 toODC without adding additional fiber.

The next evolution of the cable access network is to distribute some ofits functions down to remote locations like the fiber node. Thisevolution is referred to generally as a distributed architecture; whensome or all of the CCAP is distributed into the network, also referredto as a distributed CCAP Architecture (DCA). Distributed CCAParchitectures extend the reach of the digital medium which providesperformance gains that are helpful in getting to higher order DOCSISmodulation (e.g., CCAP-ARCH).

There are three distributed architectures that have been defined so far:remote-physical layer (R-PHY); remote-media access control PHY(R-MACPHY); and split-media access control (Split-MAC). In someembodiments, Remote-MACPHY moves the entire CMTS/CCAP into a device thatsits at a remote node, referred to as a R-MACPHY device (or RMD). R-PHYsplits the CMTS between the MAC layer and PHY layer and moves the PHYlayer to a remote node; the device at the hub that retains the MAC layeris referred to as a CCAP-Core, and the device that sits at the RemoteNode location is referred to as Remote PHY Device (RPD). Split-MAC movessome of the MAC function and all the PHY function to the remote node.

FIG. 5 is a schematic illustration of a remote network architecture 500.Architecture 500 represents a PHY architecture, and is similar to, insome respects, architecture 300, FIG. 3. That is, architecture 500includes a hub 502, a node 504, a transport medium 506, a plurality ofend users 508, a plurality of short transport media 510, a plurality ofdeep nodes 512, and a router 516. Node 504 may be an OCD (e.g., anenclosure), or an OCD may exist elsewhere within architecture 500. Deepnodes 512 may represent a RPD, and router 516 may include a CCAP core518. In this case, architecture 500 illustrates an R-PHY architecture,and is functional to convert from a digital medium like Ethernet or PONto analog for transmission over coaxial using RF in the downstream andupstream directions.

In operation of architecture 500, the ODC, which may be located in node504, includes an Ethernet switch that receives an inbound Ethernetsignal from the CCAPMTS 414 at hub 402 and routes the Ethernet signal tothe intended RPD (e.g. located in deep node 512). The RPD terminates theEthernet signal and converts it into RF that it sends to modem at thecustomer premises of end user 508. A R-MACPHY architecture (not shown)is similar to architecture 500, however, a R-MACPHY architecture willtypically include an RMD instead of a RPD as deep nodes 512.

FIG. 6 is a schematic illustration of a passive optical network (PON)architecture 600. Architecture 600 similar to, in some respects,architecture 300, FIG. 3, and includes a hub 602, a node 604, atransport medium 606, a plurality of end users 608, and a plurality ofshort transport media 610. Different from the configuration illustratedin FIG. 3, architecture 600 includes an optical line terminal (OLT) 614at hub 602. Additionally, a plurality of optical network units (ONUs)608 are coupled to transport media 610 at or near the customer premisesof end users.

In some cases, such as areas with new construction, cable operators maybuild purely fiber networks rather than HFC networks using PONtechnologies. PON architecture 600 supports fiber 606 and/or 610 to endusers (e.g., a residential customer (FTTH), a business (FTTB), smallcell (FTTC), base station or tower (FTTT)). Architecture 600 includesOLTs at hub 602, optical splitters at node 604 (i.e., the location ofthe ODC), and ONUs 608 at or near the customer premises of endpoints/endusers. Architecture 600 may service 16-32 ONUs. A digital PONarchitecture, such as architecture 600 may have some limitation, suchas, for example, digital PON architecture traditionally supports no morethan 20 km between the OLT 614 and ONU at the premises of end user 608,because of the signal loss that occurs from attenuation of the fiber andby using only passive components like optical splitters.

FIG. 7 is a schematic illustration of a remote passive optical networkarchitecture 700. Architecture 700 is a remote PON architecture, and issimilar to, in some respects, architecture 300 (FIG. 3). Architecture700 includes a primary hub 702, a node 704, a transport medium 706, aplurality of end users 708, a plurality of short transport media 710,and a router 714. Different from the configuration illustrated in FIG.3, architecture 700 further includes a plurality of OLTs 712 downstreamof node 704 and upstream from end users 708. As illustrated in FIG. 7,architecture 700 further forms a virtual hub 718 that includes node 704and one or more OLTs 712. A plurality of ONUs is respectively coupled totransport media 710 at or near the premises of end users 708.

As described above, digital PON traditionally supports no more than 20km between the OLT and ONU, because of the signal loss that occurs fromattenuation of the fiber and by using only passive components likeoptical splitters. To overcome this limitation, operators can deployRemote PON, or R-PON, architectures, such as architecture 700, to moveOLT 712 out of primary hub 702 to a cabinet within virtual hub 718. OLT712 is typically located less than 20 km from an ONU at the premises ofan end user 708. By combining multiple wavelengths onto fiber 706 fromhub 702 to virtual hub 718, virtual hub 718 can contain multiple OLTs712, one for each wavelength. As shown in FIG. 7, virtual hub 718contains a remote OLT 712 as well as an element that decomposes thesingle fiber back into individual wavelengths with one wavelength perfiber, where each fiber 710 connects to a remote OLT 712. In someembodiments, the decomposition back into individual wavelengths many beperformed by an Ethernet Switch as shown in FIG. 7. In some cases amuxponder or demultiplexer is alternatively employed. If the remote OLT712 happens to reside in the same cabinet or chassis as the Ethernetswitch, there could be an electrical interface from the switch to remoteOLT 714 instead of fiber. In some embodiments, remote OLT 714 is locatedwithin virtual hub 718, but the remote OLT could be deeper in the accessnetwork to maintain the maximum 20 km distance between OLT and ONU. Aswith the case of traditional PON (e.g., FIG. 6), each remote OLT 714 canservice 16 to 32 ONU at the premises of an end user 708.

FIG. 8 is a schematic illustration of a network architecture 800.Architecture 800 represents an Ethernet private line (EPL) architecturedelivering P2P Ethernet over fiber, and is similar to, in some respects,architecture 200, FIG. 2, and includes a hub 802, a node 804, atransport medium 806, a plurality of end users 808, a plurality of shorttransport media 810, one or more amplifiers 812, and a router 816. Asshown in FIG. 8, end users 808(1)-(4) are businesses and transport media806 are directly communicatively coupled between hub 802 and end users808(1)-(4).

As described above, HFC networks have been designed with a small number(6-8) of fiber strands dedicated to each node. These fibers may havebeen repurposed for business services, such as EPL or Ethernet VirtualPrivate Line (EVPL), while others may have been sold as dark fiber forthe business that has total control of the fiber. In the Ethernetservice illustrated in FIG. 8, hub 802 connects directly to the premiseof one or more end users 808 (e.g., a business) over fiber 806 by usingspare fibers or by repurposing and extending a fiber that was deployedto a node 804 as shown in FIG. 8.

FIG. 9 is a schematic illustration of a network architecture 900.Architecture 900 is an EPL architecture similar to architecture 800,FIG. 8, except that architecture 900 additionally featuresimplementation of a multiplexer. More particularly, architecture 900includes a hub 902, a node 904, a transport medium 906, a plurality ofend users 908, a plurality of short transport media 910, a plurality ofamplifiers 912, and a router 916. As illustrated in FIG. 9, end users908 are depicted as businesses, and transport media 806 are connecteddirectly to the premises thereof. Architecture 900 further includes amultiplexer 918 and a demultiplexer 920. Multiplexer 918 is connectivelycoupled to upstream to router 916 at hub 902 and connectively coupleddownstream to transport medium 906. Demultiplexer 920 is connectivelycoupled to transport medium 906 at node 904 and downstream to end users908 through a plurality of downstream fibers 922. In operation ofarchitecture 900, demultiplexer 920 splits multiple wavelengths ontotheir own respective downstream fiber 922 and/or onto the samedownstream fiber 922. Specifically, as shown in FIG. 9, downstreamfibers 922(1)-(4) each receive their own wavelengths and are connectedto end user/businesses 908(1)-(4). The remaining wavelengths travelthrough fiber 922(5) to node 904.

Where there is scarcity of fiber, an operator may use wavelengthmultiplexer 918 at HE/Hub 902 and demultiplexer 920 at the virtual hub(i.e., at node 904) to split the single fiber from the HE/Hub intomultiple fibers that connect to businesses. This the type ofconfiguration represents a more cost-effective use of the fiber fromHE/Hub to virtual hub than retrenching. However, non-coherent opticallinks, including those having very high capacity, use the wavelengthspectrum thereof very inefficiently. Additionally, significantoperational complexity is added by meeting to manage many wavelengths,which limits the capacity of the network as the demand increases.Complicating the problem further, the coexistence of non-coherentwavelengths with potentially different technologies (e.g., analog opticsand EPON) on the same fiber will further limit the total number ofwavelengths available to the non-coherent system, in order to avoidinterfering with the coexisting wavelengths.

FIG. 10 is graphical illustration of a service bandwidth growth plot1000. As illustrated in FIG. 10, service demand in the access network issteadily increasing, driven by a variety of factors. Operators perceivethat the demand for additional service bandwidth to the user is causedby technology advances. As the demand for service bandwidth increases,the access network capacity needs to increase similarly.

As the Internet of Things (IoT) expands to more Internet-connecteddevices, such as Smart Homes or Smart Buildings, the IoT will drive theneed for more bandwidth in the access network primarily from the verylarge number of devices that are deployed worldwide. However, there willbe some devices, such as video doorbells and other video securitydevices that transmit to mobile or desktop devices that will onlyrequire large amounts of bandwidth periodically. Other industries, suchas healthcare, will rely on the access network to make the IoT bereliable and responsive. As more medical devices connect to theInternet, these devices may need little bandwidth. However, the sheernumber of such devices might consume the entirety of the access networkcapacity. Healthcare deployments will also require the Access network tohave large bandwidth to exchange large data files across the Internet innear real-time for collaboration among healthcare providers in differentlocations.

Virtual Reality (VR) is also becoming more prevalent, especially in themobile and gaming sectors, which will require large bandwidth todownload the applications and environments. Eventually, it is expectedthat VR will become more interactive among two or more users that aresharing the experience together. Additionally, retail companies arepioneering into Augmented Reality (AR) to allow potential customers toexperience a product before purchasing online. As VR and AR applicationsbecome more prevalent, it will drive the need for higher bandwidth inthe Access network with low latency to make the experience feelrealistic to users.

For television applications, the present trend is moving toward higherdefinition (e.g., Ultra HD of 4 k or 8 k) display, and for streamingover the Internet (IP TV). The combination of these two technologieswill drive higher bandwidth and lower latency requirements onto theaccess network. In addition to receiving TV from the Cloud, more endusers are relying on the Cloud as a storage for data, which can often bevery large. There is also a move toward Fog Computing, as well as theprocessing of data on smart devices instead of in the Cloud. Sensorscould send the data across the access network to the smart device for itto process, interpret, and display the data to the user on the smartdevice. The smart device in turn could summarize the data and send it tothe Cloud for trending or long-term storage to free up space on thedevice itself.

As end users begin combining some of these technologies together, suchas streaming Ultra HD VR from the Cloud, it will increasingly drive moreneed for bandwidth and low latency in the access network. The combinedservices will also enable new or expanding services for an operator,such as Small Cell and Base Station backhaul/fronthaul to deliver theneeded bandwidth to the mobile end users. Finally, to compete withtelecoms offering Fiber-to-the-Home (FTTH) and Fiber-to-the-Business(FTTB), cable operators are expanding their fiber reach as well. Thereis a natural evolution of the access network to lower the cost per bitand reduce operational complexity.

For these reasons and others, capacity demand in the access network willcontinue to increase, and cable operators will need cost effective meansof doing so. As as described above, cable operators are addressing thisincreasing demand by splitting nodes and pushing fiber deeper into thenetwork, as well as deploying distributed architectures. However, withthe limited fiber available between the HE/hub and existing fiber nodelocations, the current technology of choice—10 Gbps direct-detectioncombined with DWDM—is rapidly becoming cost-prohibitive, and provides along term limit on network capacity. Trenching/retrenching new fiber isin even more expensive option, and therefore even less desirable.Accordingly, both embodiments provide significantly cost-effectivesolutions through the implementation of coherent optic technology intoexisting and future network architectures.

Coherent optics implements techniques for using the modulation and phaseof light, as well as two different light polarizations, to transmitmultiple bits per symbol over fiber transport media. There are severalefficient modulation formats such as M-ary phase shift keying (QPSK, forexample) and quadrature-amplitude-modulation (QAM). The coherentmodulation formats have an in-phase (I) amplitude component and aquadrature phase (Q) amplitude component.

FIG. 11 is graphical illustration depicting a polarization multiplexingeffect 1100. As shown in FIG. 11, a particular modulation format May becarried across two different polarizations that are orthogonal to oneanother, for example, linearly polarized signals represented aspolarization X and polarization Y, thereby producing polarizationmultiplexing effect 1100.

A basic coherent optic link includes a transmitting end, a receivingend, and a transport medium/fiber therebetween. The coherent optic linkis bidirectional, in that it may use the same wavelength fortransmitting that it uses for receiving as long as the link is over twofibers. In this case, a coherent optic transceiver uses the same laserfor transmitting as it does for receiving (e.g., a local oscillator, orLO). In the case of a single fiber, the Coherent Optic Link uses adifferent wavelength for sending than it does for receiving, so theCoherent Optic Transceiver needs 2 different lasers, one for eachdirection.

FIG. 12 is graphical illustration depicting a visualization 1200 of adata channel. In exemplary operation, the coherent optic transmitterreceives data from its Host and maps the data into the symbol based onmodulation format. If the transmitter uses polarization multiplexing(PM), it maps two consecutive constellations onto the two polarizations(I/Q-X, I/Q-Y), and then multiplexes the two polarizations. Thetransmitter may thus transmit two constellations simultaneously per timeslice, thereby doubling the number of bits sent per symbol. Thetransmitter also controls the number of symbols it sends per secondexpressed as the symbol rate. The symbol rate relates to the bits/secondthe transmitter sends for each modulation format as determined by thenumber of bits per symbol and symbols per time slice. Accordingly, toincrease the bit rate, the transmitter can either use a densermodulation format or it can increase the symbol rate.

For example, using 16-QAM modulation format with 4 bits per symbol andmultiplexing the two polarizations at 32 G-symbols per second, a singlewavelength can achieve 256 Gbps per channel. In another example, byusing WDM configuration with eight wavelengths of each 256 Gbps, the rawbit rate across the fiber can reach 2048 Gbps (2.048 Tbps). Thus, eachdata channel contains two polarization tributaries. Each polarizationcontains In-Phase and Quadrature components. Each symbol has a definedduration determined by the symbol rate. The number of bits per timeslice ranges from two bits (e.g., QPSK with single polarization) up toeight bits (16QAM with two polarizations). Visualization 1200illustrates these relationships for a 16QAM modulation format having twopolarizations.

In the case where PM is used, the coherent optics receiver separates thetime slice into each polarization (I/Q-X, I/Q-Y), and then demodulatesthe received signal for each phase into the separate I and Q componentsusing an LO. Once the receiver converts the analog signal to digital,the receiver may employ digital signal processing (DSP) and/orinexpensive filters to remove the signal distortions introduced alongthe path. Ultimately, the coherent optic receiver retrieves the dataencoded in the symbol and passes that onto the Host.

FIG. 13 is a schematic illustration of a coherent network architecture1300. Architecture 1300 illustrates high-level functions of a coherenttransmitter 1302 and a coherent receiver 1304. A transport medium 1306(e.g., an optical fiber) is communicatively coupled between coherenttransmitter 1302 and coherent receiver 1304. Coherent transmitter 1302includes an optical source 1308 coupled to an I/Q modulator 1310, whichis directly or indirectly coupled with transport medium 1306. Coherentreceiver 1304 includes an optical hybrid unit 1312, coupled to transportmedium 1306, an optical receiver 1314, and an optical local oscillator1316. Optical receiver 1314 is further be coupled to a signal processingmodule 1318.

In operation, coherent transmitter 1302 takes in data and maps the datainto the modulation format using the four degrees of freedom (I, Q, X,Y) to create the time slice transmitted over medium/fiber 1306. Coherentreceiver 1304 then detects the time slice and demodulates it to retrievethe data. Architecture 1300 is provided for illustrative purposes, andis not intended to be limiting. Architecture 1300 may include a numberof additional components that are not depicted.

Conventional analog and non-coherent optical technology used in accessnetworks are limited on how much bandwidth a single fiber can support(usually 10 Gbps or less per wavelength). To achieve greater bandwidthrequires more wavelengths and eventually more fiber strands. In manycases, retrenching as required to add the additional strands. Thepresent embodiments illustrate how coherent optics technology andcoherent optics P2P links may significantly increase the bandwidthdelivered over the existing fiber, thereby avoiding the need forretrenching.

Most cable access networks between HE/hub and ODC/fiber node are lessthan 100 km with many less than 40 km. Therefore, the access networkdoes not need some of the components needed for long-haul and metrocoherent networks. These other coherent networks require amplifying thesignal between transceivers and use more expensive components to dealwith the distortion of the signal, such as chromatic dispersion (CD) andpolarization mode dispersion (PMD), that worsen with distance. Withshorter distances to fiber nodes that are in 10's of km instead of 100'sor 1000's of km, P2P coherent optics for the access network is lesscomplex than metro and long haul, so it can use less complex componentsincluding less expensive DSPs. Less complex components consume loweroptical power that results in lower heat dissipation for transmittingand receiving signals. With less complex components, implementations canuse common components instead of proprietary components, which shouldlead to interoperability between vendors. Therefore, P2P coherent opticsdelivers a lower cost per bit in the access network than in thelong-haul and metro networks, while leveraging similar technology.

The shorter distances of the present embodiments result in fewer signaldistortions, especially when using unamplified links. For instance,there is almost no chromatic dispersion for distances less than 100 km,and what there is can easily be corrected for with a DSP or inexpensivefilter. With less severe distortions, P2P coherent optics for accessnetworks has better Signal to noise ratio (SNR) that allows for highermodulation orders than the other networks, which leads to more efficientuse of the fiber. The simpler design results in a more scalable network.For instance, the P2P coherent optics transceiver will be able toprovide 100, 200, or even 400 Gbps per wavelength. Because of the higherspectral efficiency, P2P coherent optics in the access network providesincreased bandwidth over the existing fiber infrastructure between theHE/hub and ODC/fiber nodes, which avoids the cost of retrenching. Byusing WDM, P2P coherent optics future-proofs the access network bysupporting multiple 100-200 Gbps (or higher) wavelengths on a singlefiber at a higher density than competing technologies. WDM also allowsP2P coherent optics to coexist with analog, non-coherent, and PONtechnologies to enable a smooth transition for an operator.

The present systems and methods that introduce P2P coherent optics intothe access network represent a progression of optical and electronicstechnologies that are moving to photonic integrated circuits (PIC) andcomplementary metal-oxide-semiconductor (CMOS) implementations that addmore functionality to the transceiver component. Section P2P coherentoptics use cases shows how P2P coherent optics can augment many of theproposed future P2P architectures to provide the most bandwidth at thelowest cost. Additionally, the present P2P coherent optics use cases mayuse muxponders instead of more expensive Ethernet switches at the ODC tolower costs even further. While other optical technologies arechallenged to meet the full DOCSIS 3.1 capabilities (e.g., full duplex),the P2P coherent optics systems and methods described herein easily meetsuch requirements.

FIG. 14 depicts a spectral band diagram 1400. More particularly, diagram1400 illustrates different spectral bands, including an original O band1402, a water peak E band 1404, an S band 1406, a C band 1408, an L band1410, and an ultra-long wavelength U band 1412. O band 1402 includeswavelengths from 1260 to 1360 nm, and represents a PON upstream band. Eband 1404 includes wavelengths from 1360 to 1460 nm. S 1406 bandincludes wavelengths from 1460 to 1530 nm, and represents the PONdownstream band. C band 1408 includes wavelengths from 1530 to 1565 nm,exhibits the lowest attenuation, and represents the original dense WDM(DWDM) band. L band 1410 includes wavelengths from 1565 to 1625 nm, haslow attenuation, and represents an expanded DWDM band. U band 1412includes wavelengths from 1625 to 1675 nm.

The P2P coherent optics solution targets C-band spectrum 1408. However,other services are already using parts of the C-band 1408, so not allwavelengths will be available to the P2P Coherent Optics solution whencoexisting with other technologies on the same fiber. FIG. 14 shows ahigh level diagram of what wavelengths make up C-band 1408. For theinitial deployment, operators would like to reuse existing WDM equipmentthat uses 100 GHz spacing between channels within C-band 1408. AlthoughC-band 1408 is the initially targeted spectrum, it may be possible inthe future to expand P2P coherent optics for the access network intopart of the L-band 1410 to further increase the bandwidth a single fibercould support.

Accordingly, the systems and methods herein for deploying coherentoptics in the access network enables increased bandwidth by reusingcoherent optics technology developed for metro and long-haul networks.However, as described herein, because of the shorter distancessupported, coherent optics for access network architectures provides asignificantly less expensive and less complex option than for metro orlong-haul networks.

The present embodiments illustrate two primary use cases for P2Pcoherent optics that operators may use to provide services: (1) anaggregation use case; and (2) an edge-to-edge (E2E) use case, where eachP2P coherent optic link may be 100 Gbps or 200 Gbps. The aggregation usecases support both distributed CCAP (R-PHY) and R-PON architectures.

There are two primary aggregation configurations: (i) one for RemotePON; and (ii) another for distributed CCAP architectures. For eitherconfiguration, a host at the virtual hub/ODC will terminate thedownstream P2P coherent optic link that originated at the HE/hub, suchas by an Ethernet switch or muxponder.

FIG. 15 is a schematic illustration of a coherent optics link subsystem1500. Subsystem 1500 represents a 100G P2P coherent optic link toEthernet switches to 10G links. Subsystem 1500 includes a coherent link1502 connectively coupled to a coherent transceiver 1504 and an Ethernetswitch 1506 connectively coupled downstream of coherent transceiver 1504by a transport medium 1508. Ethernet switch 1506 is further coupled to aplurality of links 1510. In the example illustrated in FIG. 15, Ethernetswitch 1506 is coupled to ten links 1510. In operation of subsystem1500, 100G coherent link 1502, coupled to coherent transceiver 1504, isthen split into ten 10G links 1510 by Ethernet switch 1506. In thisexample, one of links 1510 is a local electrical link 1510(10).

FIG. 16 is a schematic illustration of the coherent optics linksubsystem 1600. Subsystem 1600 is similar to subsystem 1500, FIG. 15,but represents a 200G P2P coherent optic link. Subsystem 1600 includes acoherent link 1602, a coherent transceiver 1604, a transport medium1606, an Ethernet switch 1608, and links 1610. In this embodiment,Ethernet switch 1606 is coupled to eight individual links 1610. Inoperation of subsystem 1600, a 200G coherent link 1602, coupled tocoherent transceiver 1604, is split into eight 25G links 1610 byEthernet switch 1606. In this example, one of links 1608 is a localelectrical link 1610(8).

FIG. 17 is a schematic illustration of a coherent optics link subsystem1700. Subsystem 1700 represents a 100G P2P coherent optic link, andincludes a coherent link 1702 communicatively coupled to a muxponder1704. Muxponder 1704 is further coupled to a plurality of links 1706. Inthe embodiment illustrated in FIG. 17, muxponder 1704 is coupled to tenindividual links 1706. In operation of subsystem 1700, 100G coherentlink 1702 provides a coherent signal to muxponder 1704, and muxponder1704 splits the received signal from coherent link 1702 into tenindividual 10G links 1706.

FIG. 18 is a schematic illustration of a coherent optics link subsystem1800. Subsystem 1800 represents a 200G P2P coherent optic link, andincludes a coherent link 1802, a muxponder 1804, and links 1806. Inoperation of subsystem 1800, 200G coherent link 1802 provides a coherentsignal to muxponder 1804 and muxponder 1804 splits the received signalfrom coherent link 1802 into eight individual 25G links 1806.

Accordingly, an Ethernet switch subsystem may support individual 10G(e.g., FIG. 15) or 25G (e.g., FIG. 16) outputs to optical links orelectrical links for elements that are co-located with the Ethernetswitch. The Ethernet switch may also be used to aggregate 10G links thatexceed the capacity of the P2P coherent optic link, in the case wherethe 10G links may be underutilized. A muxponder subsystem similarlysupports 10G (e.g., FIG. 17) or 25G (e.g., FIG. 18) output opticallinks. The muxponder 10G/25G output capacity is therefore equal to thecapacity of the P2P coherent optic link. In the embodiments describedabove, the incoming P2P coherent optic link is 100 Gbps or 200 Gbps, butthese links are provided for illustrative purposes, and not in alimiting sense. Future subsystems are contemplated that support 400 Gbpsand greater.

For the first aggregation use case of R-PON, one or more OLT will existat an aggregation point referred to herein as a “virtual hub.” TheEthernet switch or muxponder will interface with the remote OLT that areusually co-located in the virtual hub. The P2P coherent optic link willgo from the HE/hub device with a P2P coherent optic transmitter to theEthernet switch or muxponder with a P2P coherent optic receiver. TheEthernet Switch or muxponder will terminate the P2P coherent optic linkand perform an optical/electrical/optical process to convert the P2Pcoherent optic link into an Ethernet link.

FIG. 19 is a schematic illustration of a network architecture for apoint-to-point coherent link 1900. Link 1900 represents an aggregationuse case for a distributed CCAP architecture. Link 1900 includes a hub1902, an ODC 1904, and a transport medium 1906 communicatively coupledtherebetween. Transport medium may be a fiber, e.g., for a 100G or 200Gcoherent optic link. Link 1900 further includes a plurality of end users1908 (e.g., a small cell 1908(1), a base station 1908(2), a consumerresidence 1908(3), a business 1908(4), a data center 1908(5)). In thisembodiment, ODC 1904 includes an Ethernet switch/muxponder 1910, whichis coupled to a plurality of downstream fibers 1912.

Link 1900 further includes a plurality of OLTs 1914 and a plurality ofRPDs 1916 coupled to downstream fiber 1912, downstream from Ethernetswitch/muxponder 1910. In this example, OLTs 1914 are located at ODC1904 and are configured to individually receive 10 Gb Ethernet (GE)/40GE/100 GE optic links. OLTs 1914 are further coupled downstream to anoptical splitter 1918, which splits the signals among end users 1908. Inthe embodiment illustrated in FIG. 19, optical splitter 1918 is a 1:32splitter, and the fiber between optical splitter 1918 and end users 1908is less than 20 km and is a 10G/25G/50G/100G link. Also in this example,the link from Ethernet switch/muxponder 1910 to RPD 1916 is a 10GE/40GEoptic link. As illustrated in FIG. 19, link 1900 further forms a virtualhub 1918 that includes ODC 1904 and OLTs 1914.

The second aggregation use case for distributed CCAP uses the Ethernetswitch or muxponder at the ODC to terminate the P2P coherent optic linkfrom the HE/hub device. The Ethernet switch or muxponder converts theP2P coherent optic link into an Ethernet link to feed the RPD/RMD byperforming an optical/electrical/optical process. The Ethernet link maytransmitted at 10 Gbps, but may transmitted up to 40 Gbps. Othervariations (not shown) to this use case are contemplated, for example,where an operator extends the P2P coherent optic link all the way to theRPD/RMD and performs the coherent-to-Ethernet conversion in the RPD/RMD.

FIG. 20 is a schematic illustration of a coherent optics networkarchitecture 2000. Architecture 2000 represents an example of anaggregation use case for distributed CCAP architecture, and is similarto link 1900, FIG. 19. That is, 2000 includes a hub 2002, an ODC 2004, atransport medium 2006, a plurality of OLTs 2010, a plurality of RPDs2012, a plurality of Ethernet switches/muxponders 2014, a multiplexer2016, servers 2018, and a demultiplexer 2020 communicatively coupled totransport medium 2006 at ODC 2004. In operation, multiplexer 2016multiplexes two or more wavelengths onto transport medium 2006 anddemultiplexer 2020 de-multiplexes the received two or more wavelengthsonto discrete links before the signals travel to Ethernetswitches/muxponders 2014.

For brownfield deployments, an operator can multiplex analog signals orother digital amplitude or pulse modulated wavelengths on the same fiberas the P2P coherent optic link enable a gradual migration to P2Pcoherent optic links. Additionally, for the aggregation configurationsdescribed herein, an operator can use wavelength multiplexing ofmultiple P2P coherent optic links to provide more bandwidth at thevirtual hub/ODC. The wavelengths would be de-multiplexed prior beingreceived by the Ethernet switch or muxponder.

FIG. 21 is a schematic illustration of a coherent optics networkarchitecture 2100. Architecture 2100 represents an example of anaggregation use case for distributed CCAP architecture, and is similarto, in some respects, architecture 2000, FIG. 20. Architecture 2100includes a hub 2102, an ODC 2104, a transport medium 2106, a pluralityof end users 2108, a plurality of OLTs 2110, a plurality of RPDs 2112, aplurality of Ethernet switches/muxponders 2114, a multiplexer 2116,servers 2118, a demultiplexer 2120, and a virtual hub 2122. In theembodiment illustrated in FIG. 21, OLTs 2110 and virtual hub 2122 arelocated outside of ODC 2104. Virtual hub 2122 includes a Ethernetswitch/muxponder 2114 connectively coupled to ODC 2104 and OLTs 2114 bya downstream fiber, e.g. a 100G/200G coherent optic link and10GE/40GE/100GE fiber. The demultiplexed links may then be connecteddirectly to end users 2108 or OLTs 2110.

The second E2E use case employs a WDM at the HE/hub that combinesmultiple P2P coherent optic links onto a fiber. At the ODC, another WDMsplits the P2P coherent wavelengths for individual transport each on itsown fiber strand. The demultiplexed P2P coherent optic links may thenconnect directly to the endpoint. The P2P coherent optic links from theHE/hub may be a mix of 100 Gbps and 200 Gbps link rates. For this usecase, the P2P coherent optic transceiver they reside in a device at theendpoint, therefore the P2P coherent optic link distance is from theHE/hub all the way to the endpoint. In some cases, the aggregation linksmay be mixed with the edge-to-edge links. However, such mixedconfigurations might not include analog or non-coherent wavelengths onthe same fiber.

By varying the modulation format used and/or the symbol rate, P2Pcoherent optic transceiver should give an operator a configurable P2Pcoherent optic link of 100 Gbps, 200 Gbps, or 400 Gbps per wavelength.Initially, there could be a P2P coherent optic transceiver that onlydoes 100 Gbps in order to get a solution to the operators quickly,eventually, there will also be a P2P coherent optic transceivers for 200and 400 Gbps (note that there are a number of tradeoffs to consider toachieve the 400 Gbps that influence the acceptable solutions, such asusing multiple wavelengths, using a higher order modulation format,increasing the symbol rate, etc. that could all affect the power neededby the P2P coherent optic transmitter and receiver and could limit thedistance it could support).

By leveraging the available capacity in the C-Band through wavelengthmultiplexing, the number of wavelengths per fiber can increase tofurther grow the P2P coherent optic bandwidth without adding additionalfiber. The goal is to make the solution flexible in the bandwidthavailable over the P2P coherent optic link to allow operators to deployonly what they require.

For the P2P coherent optic link, there will often be 2 fibers betweenthe two P2P coherent optic transceivers, one for downstream/forward andone for upstream/return. However, an operator could deploy bidirectionallinks over a single fiber with optimized wavelength allocation andmitigation for backreflection, but there can be no inline amplificationon the shared fiber. The amplification would need to occur directionallyfor downstream and upstream separately, before combining on the samefiber or after splitting from the same fiber. The P2P coherent optictransceivers will be paired such that the downstream/forward andupstream/return go to the same transceiver pair. However, bidirectionallinks will require a separate laser for the LO, because the downstreamand upstream will be on different wavelengths. The P2P coherent optictransceivers generate a constant data rate in both directions, forexample, 100 Gbps downstream/forward and 100 Gbps upstream/return.

The present P2P coherent optics implementations might further vary basedon the length of the P2P coherent optic link. For example, the P2Pcoherent optic transceiver could require more power for the greaterdistances to increase the OSNR (optical signal to noise ratio) or itcould require amplifiers or other components not needed for the shorterdistances. The embodiments herein consider, by way of illustration andnot in a limiting sense, three distance ranges: 0 km to 40 km; 40 km to80 km; and 80 km to 120 km.

The present solutions optimize for distances of up to 40 km to capturegreater than 80% of the use cases. In a base configuration, essentiallyany supported data rate may work without the addition of opticalamplification. The solution for distances greater than 40 km mightdiffer though, from the <40 km solution. There are a number of differenttradeoffs that are contemplated within the present embodiments fordistances >40 km that might drive up the cost of the solution and/orlower the overall bandwidth per fiber. Rather than trying to build oneP2P coherent optic transceiver to support all the variations, theembodiments described herein illustrate optimization examples for up to40 km and then, if that does not support the longer distances, look athow an operator could modify the optimized solution for the longerdistances. Since the majority of cases (˜88%) for most operators will bebelow the 40 km limit, the number of specialized solutions should berelatively small for most operators.

A P2P coherent optic transceiver in the HE/hub will be within anenclosure that is environmentally controlled, so it would be expected tooperate within normal specifications for that type of environment. TheP2P coherent optic transceiver in the field, however, may or may not bein a controlled environment. The remote P2P coherent optic transceivercould exist on a pedestal, pole, or other enclosure that is exposed tothe weather and temperature changes. Therefore, the environmentalrequirements will vary drastically depending on where a P2P coherentoptic transceiver is deployed. These temperatures may range from as lowas −40 C to as high as +85 C. It may not be feasible for a single P2Pcoherent optic transceiver to support all conditions. However, the goalis to have an interoperable version of the P2P coherent optictransceiver that works in the majority (80%-90%) of the deploymentenvironments.

The present P2P coherent optic transceiver are configured to work withthe power available at the current fiber node location, sharing it withany other devices that may be present. Therefore, operators would liketo target 10 W to 20 W for the P2P coherent optic transceiver, includingthe optics and DSP power requirements.

FIG. 22 is a schematic illustration of a migrated coherent opticsnetwork architecture 2200. Architecture 2200 illustrates a case of acentralized network architecture coexisting with a P2P coherent opticarchitecture. Architecture 2200 includes a hub 2202, a node 2204 and atransport medium 2206 communicatively coupled therebetween. Hub 2202includes a plurality of analog fibers 2208, a coherent optic link 2210,and a multiplexer 2212. Analog fibers 2208 and coherent optic link 2210are communicatively coupled to multiplexer 2212. Node 2204 includes ademultiplexer 2214 that is communicatively coupled to a plurality ofnodes 2216 through a plurality of analog fibers 2218. Demultiplexer isfurther communicatively coupled to an Ethernet switch/muxponder 2220through a coherent optic link 2222. Coherent optic link 2222 is a100G/200G link. A plurality of RPDs 2224 are communicatively coupled toEthernet switch/muxponder 2220 downstream of Ethernet switch/muxponder2220.

Where operators want to migrate from a current architecture to a P2Pcoherent optic architecture, there could be a time when P2P coherentoptic links coexist with other intensity or phase modulated digitallinks, or an analog signal on the same fiber using differentwavelengths. Where available, an operator can use separate fiber foreach solution, and then move services off the old architecture onto theP2P coherent optic architecture in a controlled fashion. For an operatorwho does not have spare fibers available, using wavelength multiplexingand demultiplexing will allow a smooth transition.

Since many operators may already be using wavelength multiplexing forexisting services, adding a P2P coherent optic link could be trivial.However, the P2P coherent optic link would need to match the spacingsupported by the wavelength multiplexer. Additionally, operators wouldneed to do wavelength management to ensure there is no interferencebetween the channels they assign. Since operators should already bedoing this for the existing multiplexed wavelengths, adding the P2Pcoherent optic link into the mix should not be an issue. Anotherconsideration is that the existing analog optical amplifiers may notwork for the P2P coherent optic link, so operators would need to designfor that situation.

Many operators will be moving in the near future from analog to P2Pcoherent optics. During this transition, the operator could add a newwavelength for the P2P coherent optic link and multiplex it with theanalog wavelengths as shown in FIG. 23. More than likely, the operatorwill be moving one analog wavelength at a time to the p2p coherent opticlink. One option is to use one of the analog wavelengths for the P2Pcoherent optic link. This would be a flash cut of that one wavelength,so the operator would need to coordinate the cut over with the remotedevice. A more conservative approach is to add a new wavelength to thefiber for the P2P coherent optic link with a P2P coherent optictransceiver in the HE/hub and the ODC/virtual hub (or other location forthe termination point of the P2P coherent optic link). Once the operatoris comfortable with the P2P coherent optic link, the operator could thencut over the traffic on one of the analog wavelengths to the P2Pcoherent optic link by converting the fiber node from analog to RemotePHY, for example. If the operator experiences any issues with thetraffic on the P2P coherent optic link, the operator can switch thetraffic back to the analog wavelength with minimal impact.

The fiber optic strands used for P2P coherent optic links could coexistwith other intensity or phase modulated digital links, or an analogsignal on the same fiber using different wavelengths as is shown by FIG.23. This means that P2P coherent optic links should avoid using certainwavelengths normally used by these other sources. An operator could usethe remaining wavelengths for other P2P coherent optic links. Thepresent P2P coherent optic link embodiments are also configured tomanage the power budget. To support the longer distances, operators mayapply more power at the P2P coherent optic transmitter or add an opticalamplifier to increase the power of the P2P coherent optic link. However,when applying more power on the P2P coherent optic link, the more likelyit could interfere with a neighboring wavelength. Therefore, an operatormay need to manage the power budget associated with distance needed andadjust the wavelength spacing and frequencies used to avoidinter-channel interference. Over time, the anticipation is that all P2Pwavelengths will transition to P2P coherent optic links. However, untilsuch time, operators will need to manage how they add P2P coherent opticlinks onto a fiber. Initially, a small set of wavelengths using fixedlasers may be used, or a small set of wavelengths using a limitedtunable laser of 4-8 channels. Operators can influence the decisionbased on the current set of wavelengths they are using in theirnetworks.

To support the longer distances, operators may apply more power at theP2P Coherent Optic Transmitter or add an optical amplifier to increasethe power of the P2P Coherent Optic Link. However, when applying morepower on the P2P Coherent Optic Link, the more likely it could interferewith a neighboring wavelength. Since the output power of the analoglinks will be higher than the P2P Coherent Optic Link, it is more likelythat the analog signal will interfere with the P2P Coherent Optic Linkthan vice versa. Therefore, when mixing the P2P Coherent Optic Link withanalog signals, the operator must find a wavelength for the P2P CoherentOptic Link with which the analog wavelength channels will not interfere.With each conversion of an analog signal to the P2P Coherent Optic Link,the chance for interference will decrease.

More than likely, each analog wavelength went to a different Fiber Node,either colocated or in different locations (Fiber Deep Nodes) bydemultiplexing at the Fiber Node location. However, for P2P CoherentOptic Link, the signal would go through an Ethernet Switch or Muxponderto convert the P2P Coherent Optic signal into an Ethernet signal. Sincea Fiber Node only works with analog signals, the operator will need toconvert from a Centralized CCAP to a Distributed CCAP (Remote MAC/PHY)that requires an Ethernet signal.

In other cases, the operator may be converting multiple PON Links to aP2P Coherent Optic Link. The operator can use the same approach asdescribed for the analog conversion. The operator would add a newwavelength for the P2P Coherent Optic Link and then migrate each PONLink to it. At the Original Fiber Node location, the operator woulddemultiplex the P2P Coherent Optic Link into the targeted PON Links byconverting the P2P Coherent Optic signal into an Ethernet signal thatwould go to a Remote OLT for each PON Link.

Once everything converts to a single P2P Coherent Optic Link between theHE/Hub and ODC/Virtual Hub, there is not a need for the WDM. However, ifthe operator plans to add more P2P Coherent Optic Links in the future,it may make sense to leave the WDM. Additionally, the operator couldremain in the hybrid mode indefinitely, if some of the existing Analogand PON wavelengths are adequate for the traffic they are carrying.

The P2P Coherent Optic Transceiver could use tunable lasers or fixedlasers. To optimize the P2P Coherent Optic Transceiver for cost, a setof fixed lasers may be the most cost effective. There is also the optionof using tunable lasers that only support 4 to 8 wavelengths that couldalso be cost competitive, but could increase the power required.Managing fixed lasers over the entire Coherent range could becomecumbersome, and could make tunable lasers over the entire rangeattractive. However, for initial implementations that use the defineddefault P2P Coherent Optic Link(s), a fixed laser seems reasonable. Asoperators need to add P2P Coherent Optic Links, the 4 to 8 wavelengthtunable lasers could make sense. By the time an operator exceeds themaximum number of tunable wavelengths, there may be cost effectivealternatives. To combine the P2P Coherent Optic Links with otherintensity or phase modulated digital links, or an analog signal, it mayrequire a retrofit of the optical filters for these other links toscreen out the P2P Coherent Optic Links.

While some high level goals were stated regarding the distances that aP2P Coherent Optics Link will need to support, in the end whatdetermines distance will be the link budget: how much loss the systemcan tolerate, vs. how much loss is actually present. Due to the greatvariety of different network configurations that are possible, thisnumber can vary widely. This section looks at some examples to providean idea of the types of scenarios in which a P2P Coherent Optics Linkcould be used and be expected to operate. Loss can occur within thefiber as well as traversing each component in the path. There are anumber of variables that affect the loss budget: (i) the fiber itselfwill have Attenuation Loss (including splices, temperature, etc.); (ii)WDM Loss; (iii) Bidirectional Band Splitter Loss (including connectors);(vi) Optical Failover Switch/Optical Splitter Loss; (v) added SafetyMargin for other unaccounted for things that could occur between thetransmitter and receiver.

The link loss may be calculated by the following equation:

Link Loss=[fiber length (km)×0.25 dB/km of fiber attenuation]+[1dB×number of optical distribution frame]+[5 dB×number of WNM]+[2dB×number of Bidirectional band splitters]+[2 dB×number of failoverswitches]+[4 dB x number of optical splitters]+[2 dB of margin]

Increasing the transmit power into the fiber can overcome some loss, butat the expense of needing more consumed power at the HE/Hub and/or ODC.Inline optical amplifiers can help to overcome the amount of loss byamplifying the power, but also amplify the noise. The receiversensitivity must overcome the potentially weak signal received and thepotentially large amount of noise (measured as OSNR) in order for thesolution to work.

The amount of currently deployed redundancy varies by operator. Somehave nearly 100% redundancy, while others have nearly 0% redundancy.However, with the increased bandwidth offered by Coherent Optics,redundancy could increase. Additional complexity occurs when theoperator wants to use a bidirectional fiber (one wavelength forDownstream and another for Upstream on the same fiber) for both theworking and protect paths. Another wrinkle comes when the protect pathmay be longer than the working path. In some cases, amplifying bothpaths is sufficient, however, amplifiers are directional, so theexamples show one way to amplify the receive and transmit pathsindependently. All this complexity can add to the link loss that thetransmitter and receiver must overcome. Since operators are doing thistoday for analog links, the coherent link should work, because acoherent receiver has higher sensitivity than the analog receivers. Totry to verify this assumption, the following sections calculated whatthe potential link loss would be for each example architecture. Theexamples are not exhaustive, but examine some variations that are likelyto be close to what operators would deploy to see where the P2P CoherentOptic Transmitter would work without amplification and where it wouldn'twork without additional amplification. The goal being to verify that ifan existing analog link didn't require amplification that the P2PCoherent Optic Link would not require amplification either.

The example Link Budget Calculation tables in the following sections usetwo different transmitter technologies—Tx A and Tx B, which results indifferent launch power into the fiber. The numbers for the transmitpower and receiver sensitivity were taken from a vendor survey, so theyare not based on a specific vendor. The following modulation formatswere used to calculate the link loss: 100G: DP-QPSK at 28 GBaud with HDFEC; 200G: DP-QPSK at 64 GBaud with SD FEC; 200G: DP-8QAM at 42 GBaudwith SD FEC; 200G: DP-16QAM at 32 GBaud with SD FEC.

FIG. 23 is a schematic illustration of a coherent optics networkarchitecture 2300. Architecture 2300 is a 40 km dual fiber singlechannel architecture. Architecture 2300 includes a hub 2302, a node2304, and a transport medium 2306 communicatively coupled therebetween.Hub 2302 includes a hub coherent transceiver 2308, having a downstreamtransmitting portion 2310 and an upstream receiving portion 2312. Asshown in FIG. 23, node 2304 is depicted as an optical distributioncenter (“OCD”) and includes a node coherent transceiver 2314, having adownstream receiving portion 2316 and an upstream transmitting portion2318.

As shown in FIG. 23, transport medium 2306, includes a downstreamtransport medium 2320, configured to transport signals downstream, andan upstream transport medium 2322, configured to transport signalsupstream. Transport medium 2306 is about 40 km in length.

Architecture 2300 further includes an optical distribution frame 2324and a plurality of splice boxes 2326. Optical distribution frame 2320 iscoupled near hub 2302 and, in operation, is used forreceiving/transmitting the respective signals from/to node 2304. Splicebox 2326 is coupled near node 2304 and is depicted as two separatesplice boxes 2326(1) and 2326(2), namely splice box 2326(1) in thedownstream lane of downstream transport medium 2320 and splice box2326(2) in the upstream lane of second upstream transport medium 2322.In operation, splice boxes 2326 are used for transmitting/receiving therespective signals to/from node 2304.

Architecture 2300 is the simplest architecture for P2P coherent opticlink. In this example, the P2P coherent optic link uses two fibers 2320,2322 between hub 2302 and ODC 2304. The two fibers 2320, 2322 require apair of P2P coherent optic transceivers 2308, 2314 to support thebi-directional traffic. From an operator survey, nearly 40% of thedeployed optical links are dual fiber single channel.

Table 1 calculates an example link budget for 40 km dual fiber singlechannel link with one fiber for downstream and one fiber for upstream,in accordance with an embodiment of architecture 2300. The link loss isthe same for both downstream and upstream under normal conditions, butthe link budget could have 1-2 dB more loss for outdoor temperatureextremes. As Table 1 shows, both P2P coherent optic transmittersfunction at a variety of the modulation formats. This is expected, sincethis is one of the simplest architectures operators could deploy.

TABLE 1 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 OpticalDistribution 1 Frame Optical System Plant Fiber Attenuation 10 40 km0.25 dB/km Total Link 11 Margin 2 Calculated Rx Input −19 −21 −22 −21−13 −13 −14 −15 Required Rx Input −30 −28 −27 −25 −30 −28 −27 −25 RxOSNR (dB) 35 35 35 35 35 35 35 35 Link Supported? Yes Yes Yes Yes YesYes Yes Yes

FIG. 24 is a schematic illustration of a coherent optics networkarchitecture 2400. Architecture 2400 is an 80 km dual fiber singlechannel with amplifiers architecture, and is similar to, in somerespects, architecture 2300 (FIG. 23). Architecture 2400 includes a hub2402; a node 2404; a transport medium 2406; a hub coherent transceiver2408, having a downstream transmitting portion 2410 and an upstreamreceiving portion 2412; a coherent transceiver 2414, having a downstreamreceiving portion 2416 and an upstream transmitting portion 2418; adownstream transport medium 2420; an upstream transport medium 2422; anoptical distribution frame 2424; and a plurality of splice boxes 2426.

Different from the configuration in FIG. 23, in architecture 2400,transport medium 2406 is about 80 km in length while transport medium2306 is about 80 km in length. Also different from the configuration inFIG. 23, architecture 2400 includes a plurality of optical amplifiers2428. Optical amplifiers 2428 are coupled to hub 2402, and in FIG. 24,optical amplifiers 2428 are depicted as two separate optical amplifiers,with amplifier 2428(1) communicatively coupled between downstreamtransmission portion 2410 and optical distribution frame 2424 andamplifier 2428(2) communicatively coupled between optical distributionframe 2424 and upstream receiving portion 2412. In operation, opticalamplifiers 2428 provide a boost for downstream signals and are used forreapplication for upstream signals. Optical amplifiers 2828 are depictedin this example as having two separate amplifiers 2828 on the downstreamand upstream lines. Nevertheless, one of ordinary skill in the art willunderstand that this depiction is provided for illustration purposes andnot in a limiting sense. That is, in some cases, a signal opticalamplifier may perform functions on both the upstream and downstreamsignals.

Longer distances can deploy the example architecture for P2P CoherentOptic Link as shown in FIG. 26. In this architecture, the P2P CoherentOptic Link requires optical amplifiers at the HE/Hub, a booster forDownstream and a preamplifier for Upstream.

Table 2 calculates an example link budget for 80 km dual fiber singlechannel link for downstream and Table 3 for upstream, in accordance withan embodiment of architecture 2400. As shown in Tables 2 and 3, the linkloss is different for downstream and upstream, because of receiversensitivity differences attributed to the optical amplifier booster fordownstream and the optical pre-amplifier for ppstream. Further, asTables 2 and 3 show, either P2P coherent optic transmitter function fordownstream and upstream at a variety of the modulation formats.

TABLE 2 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 Post EDFA Gain −3−5 −6 Power/channel out −5 −4 −2 of EDFA (dBm) Optical Distribution 1Frame Optical System Plant Fiber Attenuation 20 80 km 0.25 dB/km ODCTotal Link 21 Margin 2 Calculated Rx Input −29 −28 −27 −25 −23 −23 −24−25 Required Rx Input −30 −28 −27 −25 −30 −28 −27 −25 Rx OSNR (dB) 35 3535 35 35 35 35 35 Calculated Rx 37.2 36.1 35.5 36.1 39.1 39.1 38.9 38.7

TABLE 3 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 Optical SystemPlant Fiber Attenuation 20 80 km 0.25 dB/km ODC Optical Distribution 1Frame Pre-EDFA Gain −11 −14 −10 −12 −2 −6 Power into EDFA −26 −28 −29−28 −21 −22 (dBm) Total Link 21 Attenuation Margin 2 Calculated Rx −18−17 −22 −19 −23 −23 −22 −19 Input Required Rx Input −18 −17 Not Not −26−24 −22 −19 Rx OSNR (dB) 15 15 15 15 20 20 20 20 Calculated Rx 19.4 17.416.4 25.3 25.3 24.3 23.4 OSNR (db) Link Supported? Yes Yes No No Yes YesYes Yes

FIG. 25 is a schematic illustration of a coherent optics networkarchitecture 2500. Architecture 2500 is a 40 km bidirectional singlechannel architecture, and is similar to, in some respects, architecture2300 (FIG. 23). Architecture 2500 includes a hub 2502; a node 2504; atransport medium 2506; a hub coherent transceiver 2508, having adownstream transmitting portion 2510 and an upstream receiving portion2512; a node coherent transceiver 2514, having a downstream receivingportion 2516 and an upstream transmitting portion 2518; an opticaldistribution frame 2524; and a splice box 2526. Transport medium 2506 isabout 40 km in length.

Different from the configuration in FIG. 23, in architecture 2500,transport medium 2506 includes a single downstream and upstreamtransport medium 2520 communicatively coupled between opticaldistribution frame 2524 and splice box 2526, rather than downstreamtransport medium 2320 and upstream transport medium 2322. Architecture2500 further includes a hub band splitter 2530 and a node band splitter2532. Hub band splitter 2530 is located within hub 2502 and iscommunicatively coupled between hub coherent transceiver 2508 andoptical distribution frame 2524. Node band splitter 2532 is locatedwithin node 2504 and is communicatively coupled between node coherenttransceiver 2514 and optical distribution frame 2526. Band splitters2530, 2532 are configured to combine/split two wavelengths ontotransport medium 2506 between hub 2502 and node 2504.

In this example, the downstream will use one wavelength and the upstreamwill use a different one. The configuration illustrated by architecture2500 requires optical bidirectional band splitters 2530, 2532 tocombine/split two wavelengths onto fiber 2520 between hub 2502 and ODC2504. From the operator survey, the weighted average for using abidirectional fiber was 21% of the time, but some operators have nearly100% bidirectional fibers.

Table 4 calculates an example link budget for 40 km single channel linkusing 1 bidirectional fiber, in accordance with an embodiment ofarchitecture 2500. The link loss is the same for both downstream andupstream, since there are no optical amplifiers used in the link. AsTable 10 shows, both P2P coherent optic transmitters will work for thislink.

TABLE 4 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 BiDi Band Splitter2 Opt Distribution 1 Frame Outside Plant Fiber Attenuation 10 40 km 0.25dB/km ODC BiDi Band Splitter 2 Total Link 15 Attenuation Margin 2Calculated Rx −23 −25 −26 −25 −17 −17 −18 −19 Input Required Rx Input−30 −28 −27 −25 −30 −28 −27 −25 Rx OSNR (dB) 35 35 35 35 35 35 35 35Link Supported? Yes Yes Yes Yes Yes Yes Yes Yes

FIG. 26 is a schematic illustration of a coherent optics networkarchitecture 2600. Architecture 2600 is an 80 km bidirectional singlechannel with amplifiers architecture, and is similar to, in somerespects, architecture 2400 and 2500 (FIGS. 24 and 25). Architecture2600 includes a hub 2602; a node 2604; a transport medium 2606; a hubcoherent transceiver 2608, having a downstream transmitting portion 2610and an upstream receiving portion 2612; a node coherent transceiver2614, having a downstream receiving portion 2616 and an upstreamtransmitting portion 2618; a single downstream and upstream transportmedium 2620; an optical distribution frame 2624; a splice box 2626; ahub band splitter 2630; and a node band splitter 2632.

Different from the configuration illustrated in FIG. 25, but similar tothe configuration shown in FIG. 24, in architecture 2600, transportmedium 2606 may be about 80 km in length. Further, architecture 2600includes a plurality of optical amplifiers 2628 coupled to hub 2602. InFIG. 26, optical amplifiers 2628 are depicted as two separate opticalamplifiers, with amplifier 2628(1) communicatively coupled betweendownstream transmission portion 2610 and hub band splitter 2630 andamplifier 2428(2) communicatively coupled between hub band splitter 2630and upstream receiving portion 2612.

For longer bidirectional links, such as the example of architecture 2600illustrated in FIG. 26, amplifiers 2428 are necessary at hub 2602. Fromthe operator survey, the operators that have nearly 100% bidirectionalfibers have <1% of those fibers at or greater than 80 km. Therefore,this example architecture 2500 may have little practical application andis provided primarily of illustrative purposes.

Table 5 calculates an example downstream link budget for 80 km singlechannel with optical amplifier booster, in accordance with an embodimentof architecture 2600. Table 6 calculates an example upstream link budgetfor 80 km single channel with optical pre-amplifier, in accordance withan embodiment of architecture 2600. As Tables 5 and 6 illustrate, thislink requires a small amount of amplification in order to close thelink. Because of optical amplifiers 2428 and the increased distance, theestimated OSNR is lower than the previous tables showed. With a lowerOSNR, it reduces the P2P coherent optic receiver sensitivity making itharder to close the link at the estimated P2P coherent optic transmitterlaunch power. However, as Tables 5 and 6 show, both P2P coherent optictransmitters should work for this example for all modulation formats.

TABLE 5 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 Post EDFA Gain −3−7 −9 −11 −1 −4 Power/ch out of −3 −1 0 3 0 2 EDFA (dBm) BiDi BandSplitter 2 Opt Distribution 1 Frame Outside Plant Fiber Attenuation 2080 km 0.25 dB/km ODC BiDi Band Splitter 2 Total Link 25 AttenuationMargin 2 Calculated Rx −30 −28 −27 −24 −27 −27 −27 −25 Input Required RxInput −30 −28 −27 −25 −30 −28 −27 −25 Rx OSNR (dB) 35 35 35 35 35 35 3535 Calculated Rx 37.2 36.1 35.5 36.1 39.1 39.1 38.9 38.7 OSNR (dB) LinkSupported? Yes Yes Yes Yes Yes Yes Yes Yes

TABLE 6 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 BiDi Band Splitter2 Opt Distribution 1 Frame Outside Plant Fiber Attenuation 20 80 km 0.25db/km ODC BiDi Band Splitter 2 Pre-EDFA Gain −15 −18 −20 −20 −1 −3 −6−10 Power into EDFA −31 −33 −34 −33 −25 −25 −26 −27 (dBm) Total Link 25Attenuation Margin 2 Calculated Rx −18 −17 −16 −15 −26 −24 −22 −19 InputRequired Rx Input −18 −17 Not Not −26 −24 −22 −19 Rx OSNR (dB) 15 15 1515 20 20 20 20 Calculated Rx 19.4 17.4 16.4 25.3 25.3 24.3 23.4 OSNR(dB) Link Supported? Yes Yes No No Yes Yes Yes Yes

FIG. 27 is a schematic illustration of a coherent optics networkarchitecture 2700. Architecture 2700 is a 40 km dual fiber multi-channelarchitecture, and is similar to, in some respects, architecture 2300(FIG. 23). Architecture 2700 includes a hub 2702; a node 2704; atransport medium 2706; a hub coherent transceiver 2708, having adownstream transmitting portion 2710 and an upstream receiving portion2712; a node coherent transceiver 2714, having a downstream receivingportion 2716 and an upstream transmitting portion 2718; a downstreamtransport medium 2720; an upstream transport medium 2722; an opticaldistribution frame 2724; and a plurality of splice boxes 2726.Additionally, transport medium 2706 is about 40 km in length.

Different from the configuration illustrated in FIG. 23, architecture2700 includes a plurality of hub multiplexers 2734 and a plurality ofnode multiplexers 2736. Hub multiplexers 2734 are coupled to hub 2702and are depicted as two separate hub multiplexers 2734, with hubmultiplexer 2734(1) communicatively coupled between downstreamtransmission portion 2710 and optical distribution frame 2724, and hubmultiplexer 2734(2) communicatively coupled between optical distributionframe 2724 and upstream receiving portion 2712. Node multiplexers 2736are coupled to node 2704 and are depicted as two separate nodemultiplexers 2736, with node multiplexer 2736(1) communicatively coupledbetween splice box 2726(1) and downstream receiving portion 2716, andnode multiplexer 2736(2) communicatively coupled between downstreamtransmission portion 2718 and splice box 2726(2). As depicted in FIG.27, multiplexers 2734, 2736 are wave division multiplexers.

Although the example architecture 2300 is possible, frequently (˜70% ofthe time according to the vendor survey), the operator will add a P2Pcoherent optic link to an existing hub 2702 that uses analog signals tothe ODC. In this case, the P2P coherent optic link will go through amultiplexer 2734, 2736 to co-exist with the analog signals, asillustrated in FIG. 27.

Table 7 calculates an example link budget for a 40 km multi-channel linkusing two fibers with one for downstream and one for upstream, inaccordance with an embodiment of architecture 700. The link loss is thesame for both downstream and upstream. As Table 7 shows, the lower powerP2P coherent optic transmitter may only work for the 100 Gbps bit rate,while the higher power P2P coherent optic transmitter should work forall modulation formats.

TABLE 7 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 WDM 5 OptDistribution 1 Frame Outside Plant Fiber Attenuation 10 40 km 0.25 dB/kmODC WDM 5 Total Link 21 Margin 2 Calculated Rx −29 −31 −32 −31 −23 −23−24 −25 Input Required Rx Input −30 −28 −27 −25 −30 −28 −27 −25 Rx OSNR(dB) 35 35 35 35 35 35 35 35 Link Supported? Yes No No No Yes Yes YesYes

FIG. 28 is a schematic illustration of a coherent optics networkarchitecture 2800.

In an embodiments, architecture 2800 is a 40 km dual fiber multi-channelwith an optical amplifier architecture, and is similar to, in somerespects, architecture 2700 (FIG. 27). Architecture 2800 includes a hub2802; a node 2804; a transport medium 2806; a hub coherent transceiver2808, having a downstream transmitting portion 2810 and an upstreamreceiving portion 2812; a node coherent transceiver 2814, having adownstream receiving portion 2816 and an upstream transmitting portion2818; a downstream transport medium 2820; an upstream transport medium2822; an optical distribution frame 2824; a plurality of boxes 2826; aplurality of hub multiplexers 2834; and a plurality of node multiplexers2836. As shown in FIG. 28, splice boxes 2826, hub multiplexers 2834 andnode multiplexers 2836 are each depicted as two separate entities, withsplice box 2826(1), hub multiplexer 2834(1) and node multiplexer 2836(1)coupled along the downstream transport medium 2820 and splice box2826(2), hub multiplexer 2834(2) and node multiplexer 2836(2) coupledalong the upstream transport medium 2824. Additionally, transport medium2806 is about 40 km in length.

Different from the configuration illustrated in FIG. 27, but similar tothe configuration shown in FIG. 24, architecture 2800 includes aplurality of optical amplifiers 2828 coupled to hub 2802. As illustratedin FIG. 28, optical amplifiers 2828 are depicted as two separateamplifiers, with one downstream amplifier 2828(1) communicativelycoupled between downstream hub multiplexer 2834(1) and opticaldistribution frame 2824, and one upstream amplifier 2828(2)communicatively coupled between optical distribution frame 2824 andupstream hub multiplexer 2834(2).

For existing links with 12 dB to 17 dB, the operator may have deployedoptical amplifiers 2828 on the fiber, as shown in FIG. 28. When adding aP2P coherent optic link to transport medium 2806, it will also gothrough an optical amplifier 2828 that supports coherent optic signals.The operators prefer to only deploy optical amplifiers 2828 in hub 2808,so on the downstream fiber 2820, optical amplifier 2828(1) boosts thesignal as it leaves hub 2802. On upstream fiber 2822, optical amplifier2828(2) acts as a preamplifier to amplify the signal as it enters theHE/Hub. In the upstream case, optical amplifier 2828(2) may be receivinga relatively noisy, weak signal. When it amplifies the signal, it alsoamplifies the noise, which could further lower the OSNR. Depending onthe type of optical amplifier 2828, the amount of gain it adds can vary.Some optical amplifiers 2828 also allow for the operator to adjust theamount of gain optical amplifier 2828 adds to the signal. This allowsthe operator to try to optimize the OSNR at upstream receiving portion2812. From the operator survey, approximately 20% of the current opticallinks use amplification to overcome the loss between the transmitter andupstream receiving portion 2812.

In order to make the link loss budget work for the low power P2Pcoherent optic transmitter for 40 km dual fiber multi-channel, opticalamplifiers 2828 are added to the links in example architecture 2800.Table 8 calculates an example downstream link budget for a 40 kmmulti-channel link using two fibers. Table 9 calculates an exampleupstream link budget for a 40 km multi-channel link using two fibers. Inthis case, the downstream uses an optical amplifier 2828 as a booster athub 2802, while the upstream uses an optical amplifier 2828 as apreamplifier in hub 2802. The power coming into preamplifier 2828 couldbe low, so the OSNR coming out of preamplifier 2828 is important for howsensitive the receiver must be to close the link. As Tables 8 and 9show, with a small amount of amplification for the 200 Gbps modulationformats, the low power P2P Coherent Optic Transmitter can now close thelink.

TABLE 8 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 WDM 5 Post EDFAGain −3 −5 −6 Power/ch out of −10 −9 −7 EDFA (dBm) Opt Distribution 1Frame Outside Plant Fiber Attenuation 10 80 km 0.25 dB/km ODC WDM 5Total Link 21 Attenuation Margin 2 Calculated Rx −29 −28 −27 −25 −23 −23−24 −25 Input Required Rx Input −30 −28 −27 −25 −30 −28 −27 −25 Rx OSNR(dB) 35 35 35 35 35 35 35 35 Calculated Rx 37.2 36.1 35.5 36.1 39.1 39.138.9 38.7 OSNR (dB) Link Supported? Yes Yes Yes Yes Yes Yes Yes Yes

TABLE 9 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 WDM 5 Outside PlantFiber Attenuation 10 40 km 0.25 dB/km ODC Optical Distribution 1 FramePre-EDFA Gain −3 −7 −10 12 −2 −6 Power into EDFA −27 −27 −24 −23 −16 −17(dBm) WDM 5 Total Link 21 Attenuation Margin 2 Calculated Rx −26 −24 −22−19 −23 −23 −22 −19 Input Required Rx Input −26 −24 −22 −19 −26 −24 −22−19 Rx OSNR (dB) 20 20 20 20 20 20 20 20 Calculated Rx 29.1 27.2 26.327.2 34.1 34.1 33.4 32.6 OSNR (dB) Link Supported? Yes Yes Yes Yes YesYes Yes Yes

FIG. 29 is a schematic illustration of a coherent optics networkarchitecture 2900. Architecture 2900 is an 80 km dual fibermulti-channel with an optical amplifier architecture, and is similar to,in some respects, architecture 2800 (FIG. 28). Architecture 2900includes a hub 2902; a node 2904; a transport medium 2906; a hubcoherent transceiver 2908, having a downstream transmitting portion 2910and an upstream receiving portion 2912; a coherent transceiver 2914,having a downstream receiving portion 2916 and an upstream transmittingportion 2918; a downstream transport medium 2920; an upstream transportmedium 2922; an optical distribution frame 2924; a plurality of spliceboxes 2926; a plurality of optical amplifiers 2928; a plurality of hubmultiplexers 2934; and a plurality of node multiplexers 2836. Differentfrom the configuration illustrated in FIG. 28, in architecture 2900,transport medium 2906 is about 80 km in length.

For longer distances, operators usually use optical amplifiers on thefiber as shown in FIG. 31. When adding a P2P Coherent Optic Link to thefiber, it will also go through an optical amplifier. The operatorsprefer to only deploy the optical amplifiers in the HE/Hub, so on theDownstream fiber, the optical amplifier will boost the signal as itleaves the HE/Hub. On the Upstream fiber, the optical amplifier will actas a preamplifier to amplify the signal as it enters the HE/Hub. In theUpstream case, the optical amplifier may be receiving a relativelynoisy, weak signal. When it amplifies the signal, it also amplifies thenoise, which could further lower the OSNR. Depending on the type ofoptical amplifier, the amount of gain it adds can vary. Some opticalamplifiers allow the operator to adjust the amount of gain the opticalamplifier adds to the signal. This allows the operator to try tooptimize the OSNR at the receiver. From the operator survey,approximately 20% of the current optical links use amplification toovercome the distance between the transmitter and the receiver.

Table 10 calculates an example downstream link budget for a 80 kmmulti-channel link using two fibers, in accordance with an embodiment ofarchitecture 2900. Table 11 calculates an example upstream link budgetfor a 80 km multi-channel link using two fibers. In this example,downstream uses optical amplifier 2928 as a booster at hub 2906, whilethe upstream uses optical amplifier 2928 as a preamplifier in hub 2906.The power coming into the preamplifier could be low, so the OSNR comingout of the preamplifier is important for how sensitive the receiver mustbe to close the link. As the downstream table shows, both P2P coherentoptic transmitters should work for all modulation formats. However, forthe upstream link, only the high power P2P coherent optic transmitterwill work.

TABLE 10 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 WDM 5 Post EDFAGain −9 −13 −15 −16 −3 −5 −7 −10 Power/ch out of −2 0 1 3 −2 0 1 3 EDFA(dBm) Opt Distribution 1 Frame Outside Plant Fiber Attenuation 20 80 km0.25 dB/km ODC WDM 5 Total Link 31 Attenuation Margin 2 Calculated Rx−30 −28 −27 −25 −30 −28 −27 −25 Input Required Rx Input −30 −28 −27 −25−30 −28 −27 −25 Rx OSNR (dB) 35 35 35 35 35 35 35 35 Calculated Rx 37.236.1 35.5 36.1 39.1 39.1 38.9 38.7 OSNR (dB) Link Supported? Yes Yes YesYes Yes Yes Yes Yes

TABLE 11 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 WDM 5 Outside PlantFiber Attenuation 20 80 km 0.25 dB/km ODC Optical Distribution 1 FramePre-EDFA Gain −20 −20 −7 −9 −12 −16 Power into EDFA −32 −34 −26 −26 −27−28 (dBm) WDM 5 Total Link 15 Attenuation Margin 2 Calculated Rx −19 −21−42 −41 −26 −24 −22 −19 Input Required Rx Input −18 −17 Not Not −26 −24−22 −19 Possible Possible Rx OSNR (dB) 15 15 15 15 20 20 20 20Calculated Rx 19.4 17.4 16.4 25.3 25.3 24.3 23.4 OSNR (dB) LinkSupported? No No No No Yes Yes Yes Yes

FIG. 30 is a schematic illustration of a coherent optics networkarchitecture 3000. Architecture 3000 is a 40 km bidirectionalmulti-channel architecture, and is similar to, in some respects,architecture 2500 (FIG. 25). Architecture 3000 includes a hub 3002; anode 3004; a transport medium 3006; a hub coherent transceiver 3008,having a downstream transmitting portion 3010 and an upstream receivingportion 3012; a node coherent transceiver 3014, having a downstreamreceiving portion 3016 and an upstream transmitting portion 3018; asingle downstream and upstream transport medium 3020; an opticaldistribution frame 3024; a splice box 3026; a hub band splitter 3030;and a node band splitter 3032. Additionally, transport medium 3006 isabout 40 km in length.

Different from the configuration illustrated in FIG. 25, but similar tothe configuration shown in FIG. 27, architecture 3000 includes aplurality of hub multiplexers 3034 and a plurality of node multiplexers3036. Hub multiplexers 3034 are coupled to hub 3002 and are depicted inFIG. 27 as two separate units, with hub multiplexer 3034(1)communicatively coupled between downstream transmission portion 3010 andhub band splitter 3030, and hub multiplexer 3034(2) communicativelycoupled between hub band splitter 3030 and upstream receiving portion3012. Node multiplexers 3036 are coupled to node 3004 and are depictedin FIG. 27 as two separate units, with node multiplexer 3036(1)communicatively coupled between node band splitter 3032 and downstreamreceiving portion 3016, and node multiplexer 3036(2) communicativelycoupled between downstream transmission portion 3018 and node bandsplitter 3032.

The example illustrated in FIG. 30 for doing multi-channel on a singlefiber requires an addition of a multiplexer along with the BidirectionalBand Splitter at the HE/Hub and the ODC.

Table 12 calculates an example link budget for a 40 km multi-channellink using one fiber with one wavelength for downstream and a differentwavelength for upstream, in accordance with an embodiment ofarchitecture 3000. The link loss is the same for both downstream andupstream. The example assumes a worst case 40 channel wave divisionmultiplexer. As the table shows, only the high power P2P coherent optictransmitter would work, but only for two modulation formats.

TABLE 12 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 WDM 5 BiDi BandSplitter 2 Opt Distribution 1 Frame Outside Plant Fiber Attenuation 1040 km 0.25 dB/km ODC BiDi Band Splitter 2 WDM 5 Total Link 25Attenuation Margin 2 Calculated Rx −33 −35 −36 −35 −27 −27 −28 −29 InputRequired Rx Input −30 −28 −27 −25 −30 −28 −27 −25 Rx OSNR (dB) 35 35 3535 35 35 35 35 Link Supported? No No No No Yes Yes No No

FIG. 31 is a schematic illustration of a coherent optics networkarchitecture 3100. Architecture 3100 is a 40 km bidirectionalmulti-channel with optical amplifiers architecture, and is similar to,in some respects, architecture 3000 (FIG. 30). Architecture 3100includes a hub 3102; a node 3104; a transport medium 3106; a hubcoherent transceiver 3108, including a downstream transmitting portion3110 and an upstream receiving portion 3112; a node coherent transceiver3114, including a downstream receiving portion 3116 and an upstreamtransmitting portion 3118; a single downstream and upstream transportmedium 3120; an optical distribution frame 3124; a splice box 3126; ahub band splitter 3130; a node band splitter 3132; a plurality ofmultiplexers 3134, depicted in this example as a downstream hubmultiplexer 3134(1) and an upstream hub multiplexer 3134(2); and aplurality of node multiplexers 3136, depicted in this example as adownstream node multiplexer 3136(1) and an upstream node multiplexer3136(2). Additionally, transport medium 3106 is 40 km in length.

Different from the configuration illustrated in FIG. 30, but similar tothe configuration in FIG. 28, architecture 3100 include a plurality ofoptical amplifiers 3128 communicative coupled between one hubmultiplexer 3134 and hub band splitter 3130. As depicted in FIG. 31,optical amplifiers 3128 include a downstream optical amplifier 3128(1)and an upstream optical amplifier 3128(2).

As mentioned above, for longer distance examples, optical amplifiers3128 may be added to the link. When that fiber is bidirectional, thepath needs to split between transmit and receive paths, because opticalamplifiers 3128 are directional. The transmit and receive paths may besplit and combined using different methods. As shown in FIG. 31,architecture 3100 uses bidirectional band splitter 3130 in hub 3102 toapply the amplification in the right direction. Hub 3102 combines allthe transmit wavelengths and amplifies them before combining them on thesame fiber where the receive wavelengths exist. On the receive path, thebidirectional band splitter separates the receive wavelengths from thetransmit wavelengths and sends the receive wavelengths through theoptical amplifier that then passes them to a WDM to split them intoindividual receive wavelengths.

Table 13 calculates an example downstream link budget for a 40 kmbidirectional multi-channel link, in accordance with an embodiment ofarchitecture 3100. Table 14 calculates an example ppstream link budgetfor a 40 km bidirectional multi-channel link, in accordance with anembodiment of architecture 3100. The downstream uses an opticalamplifier 3128(1) as a booster at hub 3102, while the upstream uses anoptical amplifier 3128(2) as a preamplifier in hub 3102. The powercoming into the preamplifier could be low, so the OSNR coming out of thepreamplifier is important for how sensitive the P2P coherent opticreceiver must be to close the link. As the tables show, by addingoptical amplifiers to the links that could not be closed in the exampleembodiment of architecture 3000, the links in both directions for allmodulation formats can be closed.

TABLE 13 A B 100G 200G 200G 200G 100G 200G 200G 200 dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM4 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 WDM 5 Post EDFA Gain−3 −7 −9 −10 −1 −4 Power/ch out of −8 −6 −5 −3 −5 −3 EDFA (dBm) BiDiBand Splitter 2 Opt Distribution 1 Frame Outside Plant Fiber Attenuation10 40 km 0.25 dB/km ODC BiDi Band Splitter 2 WDM 5 Total Link 25Attenuation Margin 2 Calculated Rx −30 −28 −27 −25 −27 −27 −27 −25 InputRequired Rx Input −30 −28 −27 −25 −30 −28 −27 −25 Rx OSNR (dB) 35 35 3535 35 35 35 35 Calculated Rx 37.2 36.1 35.5 36.1 39.1 39.1 38.9 38.7OSNR (dB) Link Supported? Yes Yes Yes Yes Yes Yes Yes Yes

TABLE 14 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM4 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 WDM 5 BiDi BandSplitter 2 Outside Plant Fiber Attenuation 10 40 km 0.25 dB/km ODCOptical Distribution 1 Frame BiDi Band Splitter 2 Pre-EDFA −7 −11 −14−16 −1 −3 −6 −10 Gain Power into EDFA −26 −28 −29 −28 −20 −20 −21 −22(dBm) WDM 5 Total Link 25 Attenuation Margin 2 Calculated Rx −26 −24 −22−19 −26 −24 −22 −19 Input Required Rx Input −26 −24 −22 −19 −26 −24 −22−19 Rx OSNR (dB) 20 20 20 20 20 20 20 20 Calculated Rx 29.1 27.2 26.327.2 34.1 34.1 33.4 32.6 OSNR (dB) Link Supported? Yes Yes Yes Yes YesYes Yes Yes

FIG. 32 is a schematic illustration of a coherent optics networkarchitecture 3200. Architecture 3200 is an 80 km bidirectionalmulti-channel with optical amplifiers architecture, and is similar to,in some respects, architecture 3100 (FIG. 31). Architecture 3200includes a hub 3202; a node 3204; a transport medium 3206; a hubcoherent transceiver 3208, having a downstream transmitting portion 3210and an upstream receiving portion 3212; a node coherent transceiver3214, having a downstream receiving portion 3216 and an upstreamtransmitting portion 3218; a single downstream and upstream transportmedium 3220; an optical distribution frame 3224; a splice box 3226; aplurality of optical amplifiers 3228, depicted in FIG. 32 as adownstream optical amplifier 3228(1) and an upstream optical amplifier3228(2); a hub band splitter 3230; a node band splitter 3232; aplurality of hub multiplexers 3234, depicted in FIG. 32 as a downstreamhub multiplexer 3234(1) and an upstream hub multiplexer 3234(2); and aplurality of node multiplexers 3236, depicted in FIG. 32 as a downstreamnode multiplexer 3236(1) and an upstream node multiplexer 3236(2).Different from the configuration illustrated in FIG. 31, in architecture3200, transport medium 3206 is about 80 km in length.

As mentioned, longer distance examples add optical amplifiers 3228 tothe link. When that fiber is bidirectional, the path needs to splitbetween transmit and receive paths, since the optical amplifiers 3228are directional. There are a few options on how to split and combine thetransmit and receive paths. The one shown in FIG. 32 uses bidirectionalband splitter in hub 3204 to apply the amplification in the rightdirection. Hub 3204 combines all the transmit wavelengths and amplifiesthem before combining them on the same fiber where the receivewavelengths exist. On the receive path, the bidirectional band splitterseparates the receive wavelengths from the transmit wavelengths andsends the receive wavelengths through the optical amplifier 3228 thatthen passes them to a WDM 3234 to split them into individual receivewavelengths.

Table 15 calculates an example downstream link budget for a 80 kmbidirectional multi-channel link, in accordance with an embodiment ofarchitecture 3200. Table 16 calculates an example upstream link budgetfor a 80 km bidirectional multi-channel link, in accordance with anembodiment of architecture 3200. The downstream uses optical amplifier3228(1) as a booster at hub 3202, while the upstream uses opticalamplifier 3228(2) as a preamplifier in hub 3202. The power coming intothe preamplifier could be low, so the OSNR coming out of thepreamplifier is important for how sensitive the P2P coherent opticreceiver must be to close the link.

TABLE 15 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 WDM 5 Post EDFAGain −13 −17 −19 −20 −7 −9 −11 −14 Power/ch out of 2 4 5 7 2 4 5 7 EDFA(dBm) BiDi Band Splitter 2 Opt Distribution 1 Frame Outside Plant FiberAttenuation 20 40 km 0.25 dB/km ODC BiDi Band Splitter 2 WDM 5 TotalLink 25 Attenuation Margin 2 Calculated Rx −30 −28 −27 −25 −30 −28 −27−25 Input Required Rx Input −30 −28 −27 −25 −30 −28 −27 −25 Rx OSNR (dB)35 35 35 35 35 35 35 35 Calculated Rx 37.2 36.1 35.5 36.1 39.1 39.1 38.938.7 OSNR (dB) Link Supported? Yes Yes Yes Yes Yes Yes Yes Yes

TABLE 16 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 WDM 5 BiDi BandSplitter 2 Outside Plant Fiber Attenuation 20 40 km 0.25 dB/km ODCOptical Distribution 1 Frame BiDi Band Splitter 2 Pre-EDFA −25 −28 −33 0−11 −13 −16 −20 Gain Power into EDFA −36 −38 −39 −38 −30 −30 −31 −32(dBm) WDM 5 Total Link 35 Attenuation Margin 2 Calculated Rx −18 −17 −13−45 −26 −24 −22 −19 Input Required Rx Input −18 −26 −24 −22 −19 Rx OSNR(dB) 15 20 20 20 20 Calculated Rx 18 13.4 12.4 34.1 34.1 33.4 32.6 OSNR(dB) Link Supported? Yes No No No Yes Yes Yes Yes

FIG. 33 is a schematic illustration of a coherent optics networkarchitecture 3300. Architecture 3300 is a redundant 40 km bidirectionalsingle channel architecture, and is similar to, in some respects,architecture 2500 (FIG. 25). Architecture 3300 includes a hub 3302; anode 3304; a transport medium 3306; a hub coherent transceiver 3308,having a downstream transmitting portion 3310 and an upstream receivingportion 3312; a node coherent transceiver 3314, having a downstreamreceiving portion 3316 and an upstream transmitting portion 3318; anoptical distribution frame 3324; a plurality of splice boxes 3326,depicted in FIG. 33 as a first splice box 3326(1) and a second splicebox 3326(2); a plurality of hub band splitters 3330, depicted in FIG. 33as a first hub band splitter 3330(1) and a second hub band splitter3330(2); and a plurality of node band splitters 3332, depicted in FIG.33 as a first node band splitter 3332(1) and a second node band splitter3332(2). Additionally, transport medium is about 40 km in length.

Different from the configuration illustrated in FIG. 25, architecture3330 includes a first upstream and downstream transport medium 3320 anda second upstream and downstream transport medium 3322. First medium3320 is commutatively coupled between coherent transceiver 3314 andfirst splice box 3326(1). Second medium 3322 is commutatively coupledbetween coherent transceiver 3314 and second splice box 3326(2). Hub3302 includes a hub optical splitter 3338 and a hub failover switch3340. Hub optical splitter 3338 is communicatively coupled to downstreamtransmission portion 3310 and hub band splitters 3330. Hub failoverswitch 3340 is communicatively coupled to upstream receiving portion3312 and hub band splitters 3330. Node 3304 a node optical splitter 3342and a node failover switch 3344. Node optical splitter 3342 iscommunicatively coupled to upstream transmission portion 3318 and nodeband splitters 3332. Node failover switch 3344 is communicativelycoupled to downstream receiving portion 3316 and node band splitters3332.

In architecture 3300, second medium 3322 is a redundant fiber extendingfrom hub 3302 to node 3304. In other embodiments, there may be a diversefiber run. In t architecture 3300, first medium 3320 is the working pathfor both downstream and upstream and second medium 3322 is the protectpath. Hub optical failover switch 3340 determines which medium 3300,3322 is used for the working path and which is used for the protectpath. Node optical splitter 3342 combines two fibers back into one fordownstream and breaks one stream into two fibers for upstream.

For shorter distances, no optical amplifiers are needed at hub 3302. AP2P coherent optic link on the fiber will work the same as other typesof links that go through an optical failover switch 3340 and opticalsplitter 3338, as shown in FIG. 35 for a redundant bidirectional singlechannel architecture.

Table 17 shows an example of the link loss for a redundant 40 kmbidirectional single channel link. As the table shows, the high powerP2P coherent optic tansmitter is the only option that will work for 200Gbps speeds without optical amplification on the link.

TABLE 17 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 Optical Splitter 4BiDi Band Splitter 2 Opt Distribution 1 Frame Outside Plant FiberAttenuation 10 40 km 0.25 dB/km ODC BiDi Band Splitter 2 OpticalFailover 2 Switch Total Link 21 Attenuation Margin 2 Calculated Rx −29−31 −32 −31 −23 −23 −24 −25 Input Required Rx Input −30 −28 −27 −25 −30−28 −27 −25 Rx OSNR (dB) 35 35 35 35 35 35 35 35 Link Supported? Yes NoNo No Yes Yes Yes Yes

FIG. 34 is a schematic illustration of a coherent optics networkarchitecture 3400. Architecture 3400 is an example of a 40 kmbidirectional multi-channel with amplification, and is similar to, insome respects, architecture 3400 (FIG. 34). Architecture 3400 includes ahub 3402; a node 3404; a transport medium 33406; a hub coherenttransceiver 3408, having a downstream transmitting portion 3410 and anupstream receiving portion 3412; a node coherent transceiver 3414,having a downstream receiving portion 3416 and an upstream transmittingportion 3418; a first upstream and downstream transport medium 3420; asecond upstream and downstream transport medium 3422; an opticaldistribution frame 3424; plurality of splice boxes 3426, depicted inFIG. 34 as a first splice box 3426(1) and a second splice box 3426(2); aplurality of hub band splitters 3430, depicted in FIG. 34 as a first hubband splitter 3430(1) and a second hub band splitter 3430(2); aplurality of node band splitters 3432, depicted in FIG. 34 as a firstnode band splitter 3432(1) and a second node band splitter 3432(2); ahub optical splitter 3438; a hub failover switch 3440; a node opticalsplitter 3442; and a node failover switch 3444.

Different from the configuration illustrated in FIG. 33, but similar insome respects to the configuration shown in FIG. 28, architecture 3400further includes a plurality of optical amplifiers 3428, depicted inFIG. 33 as a downstream optical amplifier 3428(1) and an upstreamoptical amplifier 3428(2); one or more hub multiplexers 3434, depictedin this example as a downstream hub multiplexer 3434(1) and an upstreamhub multiplexer 3434(2); and one or more node multiplexers 3436,depicted in this example as a downstream node multiplexer 3436(1) and anupstream node multiplexer 3436(2). In architecture 3400, transportmedium 33406 is about 40 km in length.

Downstream hub multiplexer 3434(1) and downstream optical amplifier3428(1) are communicatively coupled between downstream transmittingportion 3410 and hub optical splitter 3438. Upstream optical amplifier3428(2) and upstream hub multiplexer 3434(2) are communicatively coupledbetween hub failover switch 3440 and upstream receiving portion 3412.Further, downstream node multiplexer 3436(1) is communicatively coupledbetween node failover switch 3444 and downstream receiving portion 3416.Additionally, upstream node multiplexer 3436(2) is communicativelycoupled between node optical splitter 3442 and upstream transmittingportion 3418.

Architecture 3400 uses a WDM 3434 in the working and protect paths tosupport multiple wavelengths on the same fiber, as shown in FIG. 34.Optical amplifiers 3428 are used on both links to get them to close.Architecture 3400 is one of the most complex with all the differentcomponents needed and therefore has one of the most challenging linkbudgets to meet.

Table 18 shows an example downstream link loss for 40 km bidirectionalmulti-channel with optical amplifiers link loss, and Table 19 shows anexample upstream link loss. Assuming the link can achieve an OSNR of atleast 20 dB at the P2P coherent optic transceiver, then both P2Pcoherent optic transmitters could work for all modulation formats,except for the DP-16QAM at 32 GBaud on the low power P2P coherent optictransmitter. However, if the OSNR at the P2P coherent optic receiver isonly 15 for the upstream link, then only the high power P2P coherentoptic transmitter would work for the modulation format of DP-QPSK forboth 100 Gbps and 200 Gbps.

TABLE 18 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 WDM 5 Post-EDFAGain −13 −17 −20 −20 −7 −9 −12 −16 Power/ch out of 2 4 6 7 2 4 6 9 EDFA(dBm) Optical Splitter 4 BiDi Band Splitter 2 Opt Distribution 1 FrameOutside Plant Fiber Attenuation 10 40 km 0.25 dB/km ODC BiDi BandSplitter 2 Optical Failover 2 Switch WDM 5 Total Link 31 AttenuationMargin 2 Calculated Rx −26 −24 −22 −21 −26 −24 −22 −19 Input Required RxInput −26 −24 −22 −1 −26 −24 −22 −19 Rx OSNR (dB) 20 20 20 20 20 20 2020 Link Supported? Yes Yes No No Yes Yes Yes Yes

TABLE 19 A B 100G 200G 200G 200G 100G 200G 200G 200G dB of DP- DP- DP-DP- DP- DP- DP- DP- Hub Loss QPSK28 QPSK64 8QAM42 16QAM32 QPSK28 QPSK648QAM42 16QAM32 Tx Output Power −6 −8 −9 −8 0 0 −1 −2 WDM 5 OpticalSplitter 4 BiDi Band Spliter 2 Outside Plant Fiber Attenuation 10 40 km0.25 dB/km ODC Optical Distribution 1 Frame BiDi Band Splitter 2 OpticalFailover 2 Switch Pre-EDFA Gain −13 −17 −20 −20 −7 −9 −12 −16 Power intoEDFA −30 −32 −33 −32 −24 −24 −25 −26 (dBm) WDM 5 Total Link 13Attenuation Margin 2 Calculated Rx −26 −24 −22 −21 −26 −24 −22 −19 InputRequired Rx Input −26 −24 −22 −19 −26 −24 −22 −19 Rx OSNR (dB) 20 20 2020 20 20 20 20 Link Supported? Yes Yes Yes No Yes Yes Yes Yes

FIG. 35 is a schematic illustration of a coherent interface subsystem3500. Subsystem 3500 includes a MAC subsystem 3502 in operablecommunication with a PHY subsystem 3504. In this example, PHY subsystem3504 includes a multi-link gear box (“MLG”) 3506, a transmitter 3508, areceiver 3510, and a control unit 3512. In an embodiment, control unit3512 is communicatively coupled to MAC subsystem 3502, MLG 3506,transmitter 3508, and receiver 3510.

In an exemplary embodiment, interface 3500 is configured to interfacewith respect to a line side 3514, a client side 3516, and a controlinterface 3518. In this example, line side 3514 includes an opticalreceive interface 3520 and optical transmit interface 3522. Further inthis example, client side 3516 includes an electrical transmit interface3524 and an electrical receive interface 3526.

More specifically, optical receive interface 3520 represents a portionof subsystem 3500 that interfaces with transmitted upstream opticalinformation. Similarly optical transmission interface 3522 represents aportion of subsystem 3500 that transmits downstream optical information.On client side 3516, electrical receive interface 3524 represents aportion of subsystem 3500 that interfaces with transmitted electricalinformation from MAC subsystem 3502. Similarly, electrical transmitinterface 3526 represents a portion of subsystem 3500 that transmitselectrical information to MAC subsystem 3502. Control interface 2518represents the connection between MAC 3502 and control unit 3512.

As shown in FIG. 35, in an embodiment, MAC subsystem 3502 transmitssignals to and receives signals from MLG 3506 via M lanes 3528. In someembodiments, receiver 3510 transmits signals to MLG 3506 via N lanes3530 and MLG 3506 transmits signals to transmitter 3508 via N lanes3532.

In some embodiments, client mapping may be performed. In an example, aspecific client format may be obtained. The specific client format maybe an existing standard, but may alternatively be a subset of anexisting standard the client side interface 3516 needs to meet. Theclient forward error correction (FEC) termination may be 100G or 200G,and control interface 3518 is useful for determining what parameters ofthe various components are configurable. The parameters may be obtainedand set by an operations support system interface (OSSI).

In some embodiments, control interface 3518 may be configured to changethe configuration of a component. In further embodiments, controlinterface 3518 may collect data from a component. In some cases, anetwork loopback may short-circuit the PHY process by sendinginformation received back to the transmitter 3522 for transmission. Inthese embodiments, both the receive and transmit processes may beperformed before transmission of a signal. The intended use of aloopback is to allow an external entity to monitor if the opticalinterface on the transceiver is working properly. In some embodiments,the network loopback may occur during turn up. In further embodiments,the network loopback may initiate if failures suddenly begin in orderto, for example, assist in troubleshoot the cause of the failure.

In some embodiments, one or more processes may occur during a networkloopback. In further embodiments, one or more configurable parametersmay be used to establish a network loopback. In still furtherembodiments, the transceiver may collect data while in loopback in orderfor operations to pinpoint the cause of a failure.

In some embodiments, a transceiver may be placed into host loopback.While the transceiver is placed into host loopback, a number ofprocesses may be performed. In further embodiments, one or moreconfigurable parameters may establish host loopback. In still furtherembodiments, the transceiver may collect data while in loopback.

In some embodiments of lineside interface 3514, line mapping may occur.Some embodiments of line mapping may include framing, such as, forexample, an Ethernet extended sublayer for both 100G and 200G. In someembodiments, differential encoding is optional. Still furtherembodiments of line mapping may include pilot tones that can be used,for example, for synchronizing transmitter 3508 and receiver 3510. In anembodiment, the pilot tones occur every 32nd symbol. Some embodiments ofline mapping may include transparent timing. In some cases, transparentcoding is optional.

FIG. 36 is a graphical illustration depicting a symbol mappingconstellation 3600. In some embodiments, constellation 3600 represents a16QAM symbol mapping. In this example, bits 3602 are mapped onto an IQconstellation (i.e., constellation 3600). In some embodiments, the 100Gmay be DP-QPSK and the 200G may be DP-8QAM or DP-16QAM. In otherembodiments, 16QAM has the same symbol rate as QPSK. In someembodiments, 8QAM is a 40 GBaud, has greater margin, allows for 50 GHzspacing, and has less than 0.5 dBm loss for bit error rate (BER).

FIG. 37 is a graphical illustration depicting a pulse shaping effect3700. Pulse shaping effect 3700 demonstrates an exemplary embodimentwhere neighboring wavelengths may be optimally deployed on the samefiber (e.g., 50 GHz spacing, in this example).

In some embodiments, forward error correction (FEC) encoding isemployed. For example, two types of FEC encodings (i) Turbo Product Code(“TPC”) 500 mW, and (ii) HC Staircase 300 nW, may be utilized. In someembodiments, TPC is used. Some FEC encoding embodiments implement AcaciaSD as a power-efficient option, and Acacia SD TPC offers flexibility forlonger distances and multiple iterations. Some FEC embodiments utilizehard decision (HD), for example, in the case of 100G with 7% overheadfor staircase FEC. Other embodiments of FEC encoding employ TPC with 15%overhead.

In some embodiments of line mapping, various symbol rates may be used.For example, in some embodiments, 31 GBaud may be used (e.g., 100G, 200Gat 16 QAM). In other embodiments, a 40-42 GBaud may be used (e.g., 200Gat 8QAM). Symbol rates may correlate to a particular modulation formatand bits per second.

FIG. 38 is a schematic illustration of a transmitter 3800. In anexemplary embodiment, transmitter 3800 may include one or more of asignal input from media access control 3802, a Mx4 GearBox 3804,configured to perform OTN Framing and/or Ethernet mapping, a FEC coder3806, an encrypter 3808, a scrambler 3810, a symbol mapper 3812, a pulseshaper 3814, a linear and nonlinear pre-emphasis unit 3816, adigital-to-analog converter 3818, an I-Q modulator and/or polarizationcombiner 3820 and a transport medium 3822. In exemplary operation oftransmitter 3800, signal input 3802 may be proceed through one or morecomponents 3802-3820 and transmitted through transport medium 3822.

In some embodiments of transmitter 3800, IQ modulation and polarizationcombining may be performed by IQ modulator and polarizer 3820. IQmodulation and polarization is the process through which IQ symbols arecombined onto two polarizations. Transmitter X-Y skew may, in someembodiments, be performed in 1 ps. Transmitter I-Q skew may, in someembodiments, be performed in 1 ps. In an embodiment of transmitter 3800,encryption may be performed by encryption unit 3808. Transmitter 3800may support a variety of encryption algorithms, such as, for example,advanced encryption standard (AES). In some cases, encryption at thislevel of the open systems interconnection (OSI) stack is particularlycomplex, and may impact interoperability.

FIG. 39 is a schematic illustration of a scrambling unit 3900.Scrambling unit 3900 may be employed with one or more of the embodimentsdescribed herein. In an exemplary embodiment scrambling unit 3900executes scrambling algorithms to support the coherent transmitter.

FIG. 40 is a schematic illustration of a filter 4000. Filter 4000 mayalso be employed with one or more of the embodiments described herein.Filter 4000 may, for example, be deployed at one or both of the coherenttransmitter and coherent receiver. In an exemplary embodiment, filter4000 is representative of a pre-equalizer transversal filter.

FIG. 41 is a schematic illustration of a pre-equalizer unit 4100. In anexemplary embodiment, unit 4100 includes a feedforward equalizer section4102 and a feedback equalizer section 4104. Feedforward equalizersection 4102 is connected to an input 4106, and feeds into an output4108. In contrast, feedback equalizer section 4104 uses output 4108 asboth an input and an output. In the exemplary embodiment, unit 4100provides both linear and nonlinear pre-emphasis, and advantageously maybe utilized to mitigate the drawbacks of cost/band-limited componentsand their corresponding effects on roll off, micro-reflection, etc.

FIG. 42 is a schematic illustration of a receiver 4200. In an exemplaryembodiment, receiver 4200 may include one or more of a signal input froma transport medium 4202, a polarization and/or orthogonal channels fromoptical hybrid and detection unit 4204, an analog-to-digital (“ADC”)converter 4206, a deskew/orthogonality compensation unit 4208, achromatic dispersion estimator and compensator 4210, a polarization modedispersion (“PMD”) compensator and polarization demultiplexer 4212, aclock recovery unit 4214, a carrier frequency offset estimator andcompensator 4216, a carrier phase estimator and compensator 4218, asymbol de-mapper 4220, a de-scrambler 4222, a decrypter 4224, a FBCdecoder 4226, a Mx4 GearBox 4228, configured to perform OTN Framingand/or Ethernet mapping, and a media access control layer 4230. Inexemplary operation of receiver 4200, signal input from transport medium4202 may proceed through one or more components 4202-4230 andtransmitted to media access control 4230. Further, in some embodiments,signal input may cycle through a cycler 4234 from clock recovery unit4214 back to ADC unit 4206.

In some embodiments, receiver 4200 may have a minimum input power. Insome embodiments, the minimum input power is −25 dBm. In furtherembodiments, the minimum input power is −22 dBm. In some embodiment,receiver 4200 has an input range post DWDM and before pre-amplifier. Insome embodiments, this range is +2 to −15 dBm. In other embodiments,receiver 4200 has a target receiver OSNR and minimum receiver OSNR. Thetarget receive OSNR may be calculated. In some embodiments, the minimumreceiver OSNR is 16 dB. In further embodiments, the minimum receiverOSNR is 22 dB. In some embodiments, data may be captured by thecomponent used to measure the OSNR. In some embodiments, receiver 4200has a polarization dependent loss (“PDL”) tolerance. In some furtherembodiments, the PDL tolerance is 1 dB. In some embodiments, receiver4200 has an I-Q skew. In other embodiments, the I-Q skew is 1 ps. Insome embodiments, coherent detection in access network may allow for alower cost local oscillator. The use of a common laser may have benefitsfor transmitter and receivers. These benefits may, for example, behigher efficiency or lower cost.

In some embodiments of P2P coherent PHY, requirements may vary dependingon a number of factors. For example, requirements for P2P coherent PHYmay change when the distance is less than 40 km, between 40 km and 80km, or between 80 km and 120 km. In further embodiments, the modes andrequirements may be defined in such a way so as to optimize the utilityof the P2P coherent PHY. For example, the modes may be optimized in away so as to lead to less expensive components than long-haul and metrocoherent optics components.

In some embodiments, the transmitter generates a pilot tone roughlyevery 32^(nd) symbol. In some embodiments, the receiver is acapable ofreceiving a pilot tone every 32^(nd) symbol. In further embodiments, thereceiver uses the pilot tone to synchronize with the symbols sent by thetransmitter. The transmitter MUST generate a pilot tone every 32ndsymbol when sending at 100 Gbps. The transmitter MUST generate a pilottone every 32nd symbol when sending 200 Gbps. The receiver MUST becapable of receiving a pilot tone every 32nd symbol for 100 Gbps. Thereceiver MUST be capable of receiving a pilot tone every 32nd symbol for200 Gbps.

The systems and methods described herein are therefore of particularadvantage with respect to applications such as Chroma D&B, ranging, andhard coding. In the case of short fibers (e.g. fibers less than or equalto 40 km), 64 QAM may be used, and may further include a FEL harddecision, lower power, elimination of some sequences, wavelengths inether the C band or L band, narrow or broad spacing (e.g., higher QAMfor broader spacing), post-compensation, and a higher symbol rate. Inthe case of long fibers (e.g., greater than 40 km), 16 QAM may be used,and may further include a hard or soft FEL decision, higher power, allsequences, wavelengths in the C band, broader spacing, both pre- andpost-compensation, and a lower symbol rate.

Exemplary embodiments of coherent optics systems and methods forcommunication networks are described above in detail. The systems andmethods of this disclosure though, are not limited to only the specificembodiments described herein, but rather, the components and/or steps oftheir implementation may be utilized independently and separately fromother components and/or steps described herein.

Although specific features of various embodiments of the disclosure maybe shown in some drawings and not in others, this convention is forconvenience purposes and ease of description only. In accordance withthe principles of the disclosure, a particular feature shown in adrawing may be referenced and/or claimed in combination with features ofthe other drawings.

Some embodiments involve the use of one or more electronic or computingdevices. Such devices typically include a processor or controller, suchas a general purpose central processing unit (CPU), a graphicsprocessing unit (GPU), a microcontroller, a reduced instruction setcomputer (RISC) processor, an application specific integrated circuit(ASIC), a programmable logic circuit (PLC), a field programmable gatearray (FPGA), a digital signal processing (DSP) device, and/or any othercircuit or processor capable of executing the functions describedherein. The processes described herein may be encoded as executableinstructions embodied in a computer readable medium, including, withoutlimitation, a storage device and/or a memory device. Such instructions,when executed by a processor, cause the processor to perform at least aportion of the methods described herein. The above examples areexemplary only, and thus are not intended to limit in any way thedefinition and/or meaning of the term “processor.”

This written description uses examples to disclose the embodiments,including the best mode, and also to enable any person skilled in theart to practice the embodiments, including making and using any devicesor systems and performing any incorporated methods. The patentable scopeof the disclosure is defined by the claims, and may include otherexamples that occur to those skilled in the art. Such other examples areintended to be within the scope of the claims if they have structuralelements that do not differ from the literal language of the claims, orif they include equivalent structural elements with insubstantialdifferences from the literal language of the claims.

What is claimed is:
 1. A communication network, comprising: a coherent optics transmitter; a coherent optics receiver; an optical transport medium operably coupling the coherent optics transmitter to the coherent optics receiver; and a coherent optics interface including a lineside interface portion, a clientside interface portion, and a control interface portion. 